asset pipeline - Rails NoMethodError: undefined method `[]' for nil:NilClass Error while precomple for production -

i 'm using trying precompile assets prduction using

rails_env=production rake assets:precompile --trace 

but gives me error

nomethoderror: undefined method `[]' nil:nilclass 

complete logs are

/home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/sass_processor.rb:278:in `sprockets_context' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/sass_processor.rb:124:in `asset_path' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/sass_processor.rb:200:in `font_path' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/script/tree/funcall.rb:140:in `_perform' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/script/tree/node.rb:50:in `perform' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/script/tree/funcall.rb:170:in `perform_arg' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/script/tree/funcall.rb:124:in `block in _perform' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/script/tree/funcall.rb:124:in `each' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/script/tree/funcall.rb:124:in `each_with_index' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/script/tree/funcall.rb:124:in `each' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/script/tree/funcall.rb:124:in `map' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/script/tree/funcall.rb:124:in `_perform' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/script/tree/node.rb:50:in `perform' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:395:in `visit_prop' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/base.rb:36:in `visit' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:158:in `block in visit' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/stack.rb:79:in `block in with_base' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/stack.rb:115:in `with_frame' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/stack.rb:79:in `with_base' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:158:in `visit' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:502:in `block (2 levels) in visit_directive' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:502:in `map' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:502:in `block in visit_directive' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:179:in `with_environment' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:501:in `visit_directive' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/base.rb:36:in `visit' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:158:in `block in visit' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/stack.rb:79:in `block in with_base' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/stack.rb:115:in `with_frame' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/stack.rb:79:in `with_base' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:158:in `visit' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/base.rb:52:in `block in visit_children' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/base.rb:52:in `map' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/base.rb:52:in `visit_children' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:167:in `block in visit_children' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:179:in `with_environment' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:166:in `visit_children' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/base.rb:36:in `block in visit' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:186:in `visit_root' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/base.rb:36:in `visit' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:157:in `visit' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/visitors/perform.rb:8:in `visit' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/root_node.rb:36:in `css_tree' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/tree/root_node.rb:20:in `render' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sass-3.4.21/lib/sass/engine.rb:278:in `render' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/sass_compressor.rb:48:in `call' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/sass_compressor.rb:28:in `call' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/processor_utils.rb:75:in `call_processor' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/processor_utils.rb:57:in `block in call_processors' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/processor_utils.rb:56:in `reverse_each' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/processor_utils.rb:56:in `call_processors' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/loader.rb:134:in `load_from_unloaded' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/loader.rb:60:in `block in load' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/loader.rb:318:in `fetch_asset_from_dependency_cache' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/loader.rb:44:in `load' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/cached_environment.rb:20:in `block in initialize' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/cached_environment.rb:47:in `yield' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/cached_environment.rb:47:in `load' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/base.rb:66:in `find_asset' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/base.rb:73:in `find_all_linked_assets' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/manifest.rb:142:in `block in find' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/legacy.rb:114:in `block (2 levels) in logical_paths' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/path_utils.rb:225:in `block in stat_tree' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/path_utils.rb:209:in `block in stat_directory' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/path_utils.rb:206:in `each' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/path_utils.rb:206:in `stat_directory' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/path_utils.rb:224:in `stat_tree' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/path_utils.rb:228:in `block in stat_tree' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/path_utils.rb:209:in `block in stat_directory' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/path_utils.rb:206:in `each' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/path_utils.rb:206:in `stat_directory' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/path_utils.rb:224:in `stat_tree' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/legacy.rb:105:in `each' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/legacy.rb:105:in `block in logical_paths' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/legacy.rb:104:in `each' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/legacy.rb:104:in `logical_paths' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/manifest.rb:140:in `find' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/sprockets/manifest.rb:168:in `compile' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-rails-3.0.4/lib/sprockets/rails/task.rb:68:in `block (3 levels) in define' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-3.5.2/lib/rake/sprocketstask.rb:147:in `with_logger' /home/faisal/.rvm/gems/ruby-2.2.3/gems/sprockets-rails-3.0.4/lib/sprockets/rails/task.rb:67:in `block (2 levels) in define' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/task.rb:240:in `call' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/task.rb:240:in `block in execute' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/task.rb:235:in `each' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/task.rb:235:in `execute' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/task.rb:179:in `block in invoke_with_call_chain' /home/faisal/.rvm/rubies/ruby-2.2.3/lib/ruby/2.2.0/monitor.rb:211:in `mon_synchronize' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/task.rb:172:in `invoke_with_call_chain' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/task.rb:165:in `invoke' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/application.rb:150:in `invoke_task' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/application.rb:106:in `block (2 levels) in top_level' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/application.rb:106:in `each' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/application.rb:106:in `block in top_level' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/application.rb:115:in `run_with_threads' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/application.rb:100:in `top_level' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/application.rb:78:in `block in run' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/application.rb:176:in `standard_exception_handling' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/lib/rake/application.rb:75:in `run' /home/faisal/.rvm/gems/ruby-2.2.3/gems/rake-10.5.0/bin/rake:33:in `<top (required)>' /home/faisal/.rvm/gems/ruby-2.2.3/bin/rake:23:in `load' /home/faisal/.rvm/gems/ruby-2.2.3/bin/rake:23:in `<main>' /home/faisal/.rvm/gems/ruby-2.2.3/bin/ruby_executable_hooks:15:in `eval' /home/faisal/.rvm/gems/ruby-2.2.3/bin/ruby_executable_hooks:15:in `<main>' tasks: top => assets:precompile 

i trying solve last 4 days tried answer posted similar questions. have deleted .css , .js files except application.js/css, result same.

what might actual issue result still same