ruby on rails - undefined method `[]' for "jpg":Sass::Script::Value::String -

after upgrading rails 4 strange errors when trying application , running.

= favicon_link_tag "favicon.png" 

produces error:

undefined method `[]' "jpg":sass::script::value::string 

below full stacktrace produces error:

actionview (4.2.7) lib/action_view/helpers/asset_url_helper.rb:174:in `compute_asset_extname' actionview (4.2.7) lib/action_view/helpers/asset_url_helper.rb:130:in `asset_path' sprockets (3.7.0) lib/sprockets/sass_processor.rb:124:in `asset_path' sass (3.4.22) lib/sass/script/tree/funcall.rb:143:in `_perform' sass (3.4.22) lib/sass/script/tree/node.rb:58:in `perform' sass (3.4.22) lib/sass/script/tree/funcall.rb:173:in `perform_arg' sass (3.4.22) lib/sass/script/tree/funcall.rb:124:in `block in _perform' sass (3.4.22) lib/sass/script/tree/funcall.rb:124:in `each' sass (3.4.22) lib/sass/script/tree/funcall.rb:124:in `each_with_index' sass (3.4.22) lib/sass/script/tree/funcall.rb:124:in `each' sass (3.4.22) lib/sass/script/tree/funcall.rb:124:in `map' sass (3.4.22) lib/sass/script/tree/funcall.rb:124:in `_perform' sass (3.4.22) lib/sass/script/tree/node.rb:58:in `perform' sass (3.4.22) lib/sass/script/tree/list_literal.rb:63:in `block in _perform' sass (3.4.22) lib/sass/script/tree/list_literal.rb:63:in `map' sass (3.4.22) lib/sass/script/tree/list_literal.rb:63:in `_perform' sass (3.4.22) lib/sass/script/tree/node.rb:58:in `perform' sass (3.4.22) lib/sass/tree/visitors/perform.rb:397:in `visit_prop' sass (3.4.22) lib/sass/tree/visitors/base.rb:36:in `visit' sass (3.4.22) lib/sass/tree/visitors/perform.rb:160:in `block in visit' sass (3.4.22) lib/sass/stack.rb:79:in `block in with_base' sass (3.4.22) lib/sass/stack.rb:115:in `with_frame' sass (3.4.22) lib/sass/stack.rb:79:in `with_base' sass (3.4.22) lib/sass/tree/visitors/perform.rb:160:in `visit' sass (3.4.22) lib/sass/tree/visitors/perform.rb:433:in `block (2 levels) in visit_rule' sass (3.4.22) lib/sass/tree/visitors/perform.rb:433:in `map' sass (3.4.22) lib/sass/tree/visitors/perform.rb:433:in `block in visit_rule' sass (3.4.22) lib/sass/tree/visitors/perform.rb:181:in `with_environment' sass (3.4.22) lib/sass/tree/visitors/perform.rb:431:in `visit_rule' sass (3.4.22) lib/sass/tree/visitors/base.rb:36:in `visit' sass (3.4.22) lib/sass/tree/visitors/perform.rb:160:in `block in visit' sass (3.4.22) lib/sass/stack.rb:79:in `block in with_base' sass (3.4.22) lib/sass/stack.rb:115:in `with_frame' sass (3.4.22) lib/sass/stack.rb:79:in `with_base' sass (3.4.22) lib/sass/tree/visitors/perform.rb:160:in `visit' sass (3.4.22) lib/sass/tree/visitors/perform.rb:433:in `block (2 levels) in visit_rule' sass (3.4.22) lib/sass/tree/visitors/perform.rb:433:in `map' sass (3.4.22) lib/sass/tree/visitors/perform.rb:433:in `block in visit_rule' sass (3.4.22) lib/sass/tree/visitors/perform.rb:181:in `with_environment' sass (3.4.22) lib/sass/tree/visitors/perform.rb:431:in `visit_rule' sass (3.4.22) lib/sass/tree/visitors/base.rb:36:in `visit' sass (3.4.22) lib/sass/tree/visitors/perform.rb:160:in `block in visit' sass (3.4.22) lib/sass/stack.rb:79:in `block in with_base' sass (3.4.22) lib/sass/stack.rb:115:in `with_frame' sass (3.4.22) lib/sass/stack.rb:79:in `with_base' sass (3.4.22) lib/sass/tree/visitors/perform.rb:160:in `visit' sass (3.4.22) lib/sass/tree/visitors/base.rb:52:in `block in visit_children' sass (3.4.22) lib/sass/tree/visitors/base.rb:52:in `map' sass (3.4.22) lib/sass/tree/visitors/base.rb:52:in `visit_children' sass (3.4.22) lib/sass/tree/visitors/perform.rb:169:in `block in visit_children' sass (3.4.22) lib/sass/tree/visitors/perform.rb:181:in `with_environment' sass (3.4.22) lib/sass/tree/visitors/perform.rb:168:in `visit_children' sass (3.4.22) lib/sass/tree/visitors/base.rb:36:in `block in visit' sass (3.4.22) lib/sass/tree/visitors/perform.rb:188:in `visit_root' sass (3.4.22) lib/sass/tree/visitors/base.rb:36:in `visit' sass (3.4.22) lib/sass/tree/visitors/perform.rb:159:in `visit' sass (3.4.22) lib/sass/tree/visitors/perform.rb:8:in `visit' sass (3.4.22) lib/sass/tree/root_node.rb:36:in `css_tree' sass (3.4.22) lib/sass/tree/root_node.rb:20:in `render' sass (3.4.22) lib/sass/engine.rb:281:in `render' sass-rails (5.0.6) lib/sass/rails/template.rb:47:in `evaluate' tilt (2.0.5) lib/tilt/template.rb:102:in `render' sprockets (3.7.0) lib/sprockets/legacy_tilt_processor.rb:25:in `call' sprockets (3.7.0) lib/sprockets/processor_utils.rb:75:in `call_processor' sprockets (3.7.0) lib/sprockets/processor_utils.rb:57:in `block in call_processors' sprockets (3.7.0) lib/sprockets/processor_utils.rb:56:in `reverse_each' sprockets (3.7.0) lib/sprockets/processor_utils.rb:56:in `call_processors' sprockets (3.7.0) lib/sprockets/loader.rb:134:in `load_from_unloaded' sprockets (3.7.0) lib/sprockets/loader.rb:60:in `block in load' sprockets (3.7.0) lib/sprockets/loader.rb:317:in `fetch_asset_from_dependency_cache' sprockets (3.7.0) lib/sprockets/loader.rb:44:in `load' sprockets (3.7.0) lib/sprockets/cached_environment.rb:20:in `block in initialize' sprockets (3.7.0) lib/sprockets/cached_environment.rb:47:in `load' sprockets (3.7.0) lib/sprockets/bundle.rb:23:in `block in call' sprockets (3.7.0) lib/sprockets/utils.rb:196:in `dfs' sprockets (3.7.0) lib/sprockets/bundle.rb:24:in `call' sprockets (3.7.0) lib/sprockets/processor_utils.rb:75:in `call_processor' sprockets (3.7.0) lib/sprockets/processor_utils.rb:57:in `block in call_processors' sprockets (3.7.0) lib/sprockets/processor_utils.rb:56:in `reverse_each' sprockets (3.7.0) lib/sprockets/processor_utils.rb:56:in `call_processors' sprockets (3.7.0) lib/sprockets/loader.rb:134:in `load_from_unloaded' sprockets (3.7.0) lib/sprockets/loader.rb:60:in `block in load' sprockets (3.7.0) lib/sprockets/loader.rb:317:in `fetch_asset_from_dependency_cache' sprockets (3.7.0) lib/sprockets/loader.rb:44:in `load' sprockets (3.7.0) lib/sprockets/cached_environment.rb:20:in `block in initialize' sprockets (3.7.0) lib/sprockets/cached_environment.rb:47:in `load' sprockets (3.7.0) lib/sprockets/base.rb:66:in `find_asset' sprockets (3.7.0) lib/sprockets/base.rb:73:in `find_all_linked_assets' sprockets (3.7.0) lib/sprockets/manifest.rb:142:in `block in find' sprockets (3.7.0) lib/sprockets/legacy.rb:114:in `block (2 levels) in logical_paths' sprockets (3.7.0) lib/sprockets/path_utils.rb:228:in `block in stat_tree' sprockets (3.7.0) lib/sprockets/path_utils.rb:212:in `block in stat_directory' sprockets (3.7.0) lib/sprockets/path_utils.rb:209:in `each' sprockets (3.7.0) lib/sprockets/path_utils.rb:209:in `stat_directory' sprockets (3.7.0) lib/sprockets/path_utils.rb:227:in `stat_tree' sprockets (3.7.0) lib/sprockets/legacy.rb:105:in `each' sprockets (3.7.0) lib/sprockets/legacy.rb:105:in `block in logical_paths' sprockets (3.7.0) lib/sprockets/legacy.rb:104:in `each' sprockets (3.7.0) lib/sprockets/legacy.rb:104:in `logical_paths' sprockets (3.7.0) lib/sprockets/manifest.rb:140:in `find' sprockets-rails (3.2.0) lib/sprockets/railtie.rb:50:in `each' sprockets-rails (3.2.0) lib/sprockets/railtie.rb:50:in `map' sprockets-rails (3.2.0) lib/sprockets/railtie.rb:50:in `precompiled_assets' sprockets-rails (3.2.0) lib/sprockets/railtie.rb:35:in `asset_precompiled?' sprockets-rails (3.2.0) lib/sprockets/railtie.rb:251:in `block (3 levels) in <class:railtie>' sprockets-rails (3.2.0) lib/sprockets/rails/helper.rb:359:in `precompiled?' sprockets-rails (3.2.0) lib/sprockets/rails/helper.rb:363:in `raise_unless_precompiled_asset' sprockets-rails (3.2.0) lib/sprockets/rails/helper.rb:337:in `digest_path' sprockets-rails (3.2.0) lib/sprockets/rails/helper.rb:325:in `asset_path' sprockets-rails (3.2.0) lib/sprockets/rails/helper.rb:102:in `block in resolve_asset_path' sprockets-rails (3.2.0) lib/sprockets/rails/helper.rb:242:in `block in resolve_asset' sprockets-rails (3.2.0) lib/sprockets/rails/helper.rb:241:in `each' sprockets-rails (3.2.0) lib/sprockets/rails/helper.rb:241:in `detect' sprockets-rails (3.2.0) lib/sprockets/rails/helper.rb:241:in `resolve_asset' sprockets-rails (3.2.0) lib/sprockets/rails/helper.rb:101:in `resolve_asset_path' sprockets-rails (3.2.0) lib/sprockets/rails/helper.rb:79:in `compute_asset_path' actionview (4.2.7) lib/action_view/helpers/asset_url_helper.rb:135:in `asset_path' actionview (4.2.7) lib/action_view/helpers/asset_url_helper.rb:292:in `image_path' actionview (4.2.7) lib/action_view/helpers/asset_tag_helper.rb:176:in `favicon_link_tag' app/views/layouts/application.haml:6:in `_app_views_layouts_application_haml___2916998330693644908_70147654436540' actionview (4.2.7) lib/action_view/template.rb:145:in `block in render' activesupport (4.2.7) lib/active_support/notifications.rb:166:in `instrument' actionview (4.2.7) lib/action_view/template.rb:333:in `instrument' actionview (4.2.7) lib/action_view/template.rb:143:in `render' actionview (4.2.7) lib/action_view/renderer/template_renderer.rb:66:in `render_with_layout' actionview (4.2.7) lib/action_view/renderer/template_renderer.rb:52:in `render_template' actionview (4.2.7) lib/action_view/renderer/template_renderer.rb:14:in `render' actionview (4.2.7) lib/action_view/renderer/renderer.rb:46:in `render_template' actionview (4.2.7) lib/action_view/renderer/renderer.rb:27:in `render' actionview (4.2.7) lib/action_view/rendering.rb:100:in `_render_template' actionpack (4.2.7) lib/action_controller/metal/streaming.rb:217:in `_render_template' actionview (4.2.7) lib/action_view/rendering.rb:83:in `render_to_body' actionpack (4.2.7) lib/action_controller/metal/rendering.rb:32:in `render_to_body' actionpack (4.2.7) lib/action_controller/metal/renderers.rb:37:in `render_to_body' actionpack (4.2.7) lib/abstract_controller/rendering.rb:25:in `render' actionpack (4.2.7) lib/action_controller/metal/rendering.rb:16:in `render' actionpack (4.2.7) lib/action_controller/metal/instrumentation.rb:44:in `block (2 levels) in render' activesupport (4.2.7) lib/active_support/core_ext/benchmark.rb:12:in `block in ms' /users/hendricius/.rbenv/versions/2.3.1/lib/ruby/2.3.0/benchmark.rb:308:in `realtime' activesupport (4.2.7) lib/active_support/core_ext/benchmark.rb:12:in `ms' actionpack (4.2.7) lib/action_controller/metal/instrumentation.rb:44:in `block in render' actionpack (4.2.7) lib/action_controller/metal/instrumentation.rb:87:in `cleanup_view_runtime' activerecord (4.2.7) lib/active_record/railties/controller_runtime.rb:25:in `cleanup_view_runtime' actionpack (4.2.7) lib/action_controller/metal/instrumentation.rb:43:in `render' actionpack (4.2.7) lib/action_controller/metal/implicit_render.rb:10:in `default_render' actionpack (4.2.7) lib/action_controller/metal/implicit_render.rb:4:in `send_action' actionpack (4.2.7) lib/abstract_controller/base.rb:198:in `process_action' actionpack (4.2.7) lib/action_controller/metal/rendering.rb:10:in `process_action' actionpack (4.2.7) lib/abstract_controller/callbacks.rb:20:in `block in process_action' activesupport (4.2.7) lib/active_support/callbacks.rb:117:in `call' activesupport (4.2.7) lib/active_support/callbacks.rb:555:in `block (2 levels) in compile' activesupport (4.2.7) lib/active_support/callbacks.rb:505:in `call' activesupport (4.2.7) lib/active_support/callbacks.rb:92:in `__run_callbacks__' activesupport (4.2.7) lib/active_support/callbacks.rb:778:in `_run_process_action_callbacks' activesupport (4.2.7) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (4.2.7) lib/abstract_controller/callbacks.rb:19:in `process_action' actionpack (4.2.7) lib/action_controller/metal/rescue.rb:29:in `process_action' actionpack (4.2.7) lib/action_controller/metal/instrumentation.rb:32:in `block in process_action' activesupport (4.2.7) lib/active_support/notifications.rb:164:in `block in instrument' activesupport (4.2.7) lib/active_support/notifications/instrumenter.rb:20:in `instrument' activesupport (4.2.7) lib/active_support/notifications.rb:164:in `instrument' actionpack (4.2.7) lib/action_controller/metal/instrumentation.rb:30:in `process_action' actionpack (4.2.7) lib/action_controller/metal/params_wrapper.rb:250:in `process_action' activerecord (4.2.7) lib/active_record/railties/controller_runtime.rb:18:in `process_action' actionpack (4.2.7) lib/abstract_controller/base.rb:137:in `process' actionview (4.2.7) lib/action_view/rendering.rb:30:in `process' actionpack (4.2.7) lib/action_controller/metal.rb:196:in `dispatch' actionpack (4.2.7) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch' actionpack (4.2.7) lib/action_controller/metal.rb:237:in `block in action' actionpack (4.2.7) lib/action_dispatch/routing/route_set.rb:74:in `dispatch' actionpack (4.2.7) lib/action_dispatch/routing/route_set.rb:43:in `serve' actionpack (4.2.7) lib/action_dispatch/journey/router.rb:43:in `block in serve' actionpack (4.2.7) lib/action_dispatch/journey/router.rb:30:in `each' actionpack (4.2.7) lib/action_dispatch/journey/router.rb:30:in `serve' actionpack (4.2.7) lib/action_dispatch/routing/route_set.rb:817:in `call' rack-cors (0.4.0) lib/rack/cors.rb:80:in `call' warden (1.2.6) lib/warden/manager.rb:35:in `block in call' warden (1.2.6) lib/warden/manager.rb:34:in `catch' warden (1.2.6) lib/warden/manager.rb:34:in `call' rack (1.6.4) lib/rack/etag.rb:24:in `call' rack (1.6.4) lib/rack/conditionalget.rb:25:in `call' rack (1.6.4) lib/rack/head.rb:13:in `call' actionpack (4.2.7) lib/action_dispatch/middleware/params_parser.rb:27:in `call' actionpack (4.2.7) lib/action_dispatch/middleware/flash.rb:260:in `call' rack (1.6.4) lib/rack/session/abstract/id.rb:225:in `context' rack (1.6.4) lib/rack/session/abstract/id.rb:220:in `call' actionpack (4.2.7) lib/action_dispatch/middleware/cookies.rb:560:in `call' activerecord (4.2.7) lib/active_record/query_cache.rb:36:in `call' activerecord (4.2.7) lib/active_record/connection_adapters/abstract/connection_pool.rb:653:in `call' actionpack (4.2.7) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call' activesupport (4.2.7) lib/active_support/callbacks.rb:88:in `__run_callbacks__' activesupport (4.2.7) lib/active_support/callbacks.rb:778:in `_run_call_callbacks' activesupport (4.2.7) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (4.2.7) lib/action_dispatch/middleware/callbacks.rb:27:in `call' actionpack (4.2.7) lib/action_dispatch/middleware/reloader.rb:73:in `call' actionpack (4.2.7) lib/action_dispatch/middleware/remote_ip.rb:78:in `call' actionpack (4.2.7) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call' actionpack (4.2.7) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call' railties (4.2.7) lib/rails/rack/logger.rb:38:in `call_app' railties (4.2.7) lib/rails/rack/logger.rb:20:in `block in call' activesupport (4.2.7) lib/active_support/tagged_logging.rb:68:in `block in tagged' activesupport (4.2.7) lib/active_support/tagged_logging.rb:26:in `tagged' activesupport (4.2.7) lib/active_support/tagged_logging.rb:68:in `tagged' railties (4.2.7) lib/rails/rack/logger.rb:20:in `call' request_store (1.3.1) lib/request_store/middleware.rb:9:in `call' actionpack (4.2.7) lib/action_dispatch/middleware/request_id.rb:21:in `call' rack (1.6.4) lib/rack/methodoverride.rb:22:in `call' rack (1.6.4) lib/rack/runtime.rb:18:in `call' activesupport (4.2.7) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call' rack (1.6.4) lib/rack/lock.rb:17:in `call' actionpack (4.2.7) lib/action_dispatch/middleware/static.rb:120:in `call' rack (1.6.4) lib/rack/sendfile.rb:113:in `call' railties (4.2.7) lib/rails/engine.rb:518:in `call' railties (4.2.7) lib/rails/application.rb:165:in `call' rack (1.6.4) lib/rack/content_length.rb:15:in `call' puma (3.6.0) lib/puma/configuration.rb:225:in `call' puma (3.6.0) lib/puma/server.rb:578:in `handle_request' puma (3.6.0) lib/puma/server.rb:415:in `process_client' puma (3.6.0) lib/puma/server.rb:275:in `block in run' puma (3.6.0) lib/puma/thread_pool.rb:116:in `block in spawn_thread' 

has seen similar?

i ended upgrading rails 3 project rails 4. errors gone.