NoMethodError: undefined method `destroy' for nil:NilClass

[fermion]

Check full details on Airbrake: #1286217981019804288

Backtrace:

[PROJECT_ROOT]/app/controllers/assignments_controller.rb:41:in destroy
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_controller/metal/implicit_render.rb:4:in send_action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/abstract_controller/base.rb:167:in process_action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_controller/metal/rendering.rb:10:in process_action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/abstract_controller/callbacks.rb:18:in block in process_action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/callbacks.rb:502:in _run__3642285388008292489__process_action__4545793802956255209__callbacks
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/callbacks.rb:405:in __run_callback
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/callbacks.rb:385:in _run_process_action_callbacks
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/callbacks.rb:81:in run_callbacks
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/abstract_controller/callbacks.rb:17:in process_action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_controller/metal/rescue.rb:29:in process_action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_controller/metal/instrumentation.rb:30:in block in process_action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/notifications.rb:123:in block in instrument
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/notifications/instrumenter.rb:20:in instrument
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/notifications.rb:123:in instrument
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_controller/metal/instrumentation.rb:29:in process_action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_controller/metal/params_wrapper.rb:207:in process_action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activerecord-3.2.20/lib/active_record/railties/controller_runtime.rb:18:in process_action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/newrelic_rpm-3.6.2.96/lib/new_relic/agent/instrumentation/rails3/action_controller.rb:38:in block in process_action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/newrelic_rpm-3.6.2.96/lib/new_relic/agent/instrumentation/controller_instrumentation.rb:318:in perform_action_with_newrelic_trace
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/newrelic_rpm-3.6.2.96/lib/new_relic/agent/instrumentation/rails3/action_controller.rb:37:in process_action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/abstract_controller/base.rb:121:in process
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/abstract_controller/rendering.rb:45:in process
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_controller/metal.rb:203:in dispatch
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_controller/metal/rack_delegation.rb:14:in dispatch
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_controller/metal.rb:246:in block in action
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/routing/route_set.rb:73:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/routing/route_set.rb:73:in dispatch
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/routing/route_set.rb:36:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/journey-1.0.4/lib/journey/router.rb:68:in block in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/journey-1.0.4/lib/journey/router.rb:56:in each
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/journey-1.0.4/lib/journey/router.rb:56:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/routing/route_set.rb:608:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/newrelic_rpm-3.6.2.96/lib/new_relic/rack/error_collector.rb:12:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/newrelic_rpm-3.6.2.96/lib/new_relic/rack/agent_hooks.rb:18:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/newrelic_rpm-3.6.2.96/lib/new_relic/rack/browser_monitoring.rb:16:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-mobile-detect-0.4.0/lib/rack/mobile-detect.rb:164:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/sass-3.2.1/lib/sass/plugin/rack.rb:54:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/middleware/best_standards_support.rb:17:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-1.4.5/lib/rack/etag.rb:23:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-1.4.5/lib/rack/conditionalget.rb:35:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/middleware/head.rb:14:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/middleware/params_parser.rb:21:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/middleware/flash.rb:242:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-1.4.5/lib/rack/session/abstract/id.rb:210:in context
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-1.4.5/lib/rack/session/abstract/id.rb:205:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/middleware/cookies.rb:341:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activerecord-3.2.20/lib/active_record/query_cache.rb:64:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activerecord-3.2.20/lib/active_record/connection_adapters/abstract/connection_pool.rb:479:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/middleware/callbacks.rb:28:in block in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/callbacks.rb:405:in _run__1843171165011015525__call__730133861104753469__callbacks
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/callbacks.rb:405:in __run_callback
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/callbacks.rb:385:in _run_call_callbacks
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/callbacks.rb:81:in run_callbacks
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/middleware/callbacks.rb:27:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/middleware/remote_ip.rb:31:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/middleware/debug_exceptions.rb:16:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/middleware/show_exceptions.rb:56:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/railties-3.2.20/lib/rails/rack/logger.rb:32:in call_app
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/railties-3.2.20/lib/rails/rack/logger.rb:16:in block in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/tagged_logging.rb:22:in tagged
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/railties-3.2.20/lib/rails/rack/logger.rb:16:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/middleware/request_id.rb:22:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-1.4.5/lib/rack/methodoverride.rb:21:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-1.4.5/lib/rack/runtime.rb:17:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/activesupport-3.2.20/lib/active_support/cache/strategy/local_cache.rb:72:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-1.4.5/lib/rack/lock.rb:15:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/actionpack-3.2.20/lib/action_dispatch/middleware/static.rb:82:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-ssl-1.3.4/lib/rack/ssl.rb:27:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-cache-1.2/lib/rack/cache/context.rb:136:in forward
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-cache-1.2/lib/rack/cache/context.rb:143:in pass
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-cache-1.2/lib/rack/cache/context.rb:155:in invalidate
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-cache-1.2/lib/rack/cache/context.rb:71:in call!
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/rack-cache-1.2/lib/rack/cache/context.rb:51:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/railties-3.2.20/lib/rails/engine.rb:484:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/railties-3.2.20/lib/rails/application.rb:231:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/railties-3.2.20/lib/rails/railtie/configurable.rb:30:in method_missing
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/unicorn-4.7.0/lib/unicorn/http_server.rb:580:in process_client
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/unicorn-4.7.0/lib/unicorn/http_server.rb:660:in worker_loop
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/newrelic_rpm-3.6.2.96/lib/new_relic/agent/instrumentation/unicorn_instrumentation.rb:22:in call
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/newrelic_rpm-3.6.2.96/lib/new_relic/agent/instrumentation/unicorn_instrumentation.rb:22:in block (4 levels) in <top (required)>
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/unicorn-4.7.0/lib/unicorn/http_server.rb:527:in spawn_missing_workers
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/unicorn-4.7.0/lib/unicorn/http_server.rb:153:in start
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/gems/unicorn-4.7.0/bin/unicorn:126:in <top (required)>
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/bin/unicorn:23:in load
[PROJECT_ROOT]/vendor/bundle/ruby/2.1.0/bin/unicorn:23:in <main>