New to ruby, can someone help me decipher this error from console?

Question

I'm really just not sure what it means or what I'm supposed to do in order to get the webpage working on my localhost. Right now it is just showing an error that reads "We're sorry, but something went wrong." when I run rails server and open up localhost:3000 in chrome.

Here is the console output:

    Started GET "/users/sign_in" for 127.0.0.1 at 2013-07-05 12:07:07 -0400
Processing by Devise::SessionsController#new as HTML
Completed 500 Internal Server Error in 55ms

NoMethodError (undefined method `empty?' for nil:NilClass):
  actionpack (3.2.11) lib/action_view/lookup_context.rb:145:in `detail_args_for'
  actionpack (3.2.11) lib/action_view/lookup_context.rb:139:in `args_for_lookup'
  actionpack (3.2.11) lib/action_view/lookup_context.rb:109:in `find'
  actionpack (3.2.11) lib/action_view/renderer/abstract_renderer.rb:3:in `find_template'
  actionpack (3.2.11) lib/action_view/renderer/template_renderer.rb:34:in `determine_template'
  newrelic_rpm (3.5.5.38) lib/new_relic/agent/instrumentation/rails3/action_controller.rb:153:in `render_with_newrelic'
  actionpack (3.2.11) lib/action_view/renderer/renderer.rb:36:in `render_template'
  actionpack (3.2.11) lib/action_view/renderer/renderer.rb:17:in `render'
  actionpack (3.2.11) lib/abstract_controller/rendering.rb:110:in `_render_template'
  actionpack (3.2.11) lib/action_controller/metal/streaming.rb:225:in `_render_template'
  actionpack (3.2.11) lib/abstract_controller/rendering.rb:103:in `render_to_body'
  actionpack (3.2.11) lib/action_controller/metal/renderers.rb:28:in `render_to_body'
  actionpack (3.2.11) lib/action_controller/metal/compatibility.rb:50:in `render_to_body'
  actionpack (3.2.11) lib/abstract_controller/rendering.rb:88:in `render'
  actionpack (3.2.11) lib/action_controller/metal/rendering.rb:16:in `render'
  actionpack (3.2.11) lib/action_controller/metal/instrumentation.rb:40:in `block (2 levels) in render'
  activesupport (3.2.11) lib/active_support/core_ext/benchmark.rb:5:in `block in ms'
  /Users/Alex/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/benchmark.rb:296:in `realtime'
  activesupport (3.2.11) lib/active_support/core_ext/benchmark.rb:5:in `ms'
  actionpack (3.2.11) lib/action_controller/metal/instrumentation.rb:40:in `block in render'
  actionpack (3.2.11) lib/action_controller/metal/instrumentation.rb:83:in `cleanup_view_runtime'
  activerecord (3.2.11) lib/active_record/railties/controller_runtime.rb:24:in `cleanup_view_runtime'
  actionpack (3.2.11) lib/action_controller/metal/instrumentation.rb:39:in `render'
  remotipart (1.0.5) lib/remotipart/render_overrides.rb:14:in `render_with_remotipart'
  actionpack (3.2.11) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
  actionpack (3.2.11) lib/action_controller/metal/responder.rb:232:in `default_render'
  actionpack (3.2.11) lib/action_controller/metal/responder.rb:160:in `to_html'
  actionpack (3.2.11) lib/action_controller/metal/responder.rb:153:in `respond'
  actionpack (3.2.11) lib/action_controller/metal/responder.rb:146:in `call'
  actionpack (3.2.11) lib/action_controller/metal/mime_responds.rb:239:in `respond_with'
  devise (2.2.3) app/controllers/devise/sessions_controller.rb:10:in `new'
  actionpack (3.2.11) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
  actionpack (3.2.11) lib/abstract_controller/base.rb:167:in `process_action'
  actionpack (3.2.11) lib/action_controller/metal/rendering.rb:10:in `process_action'
  actionpack (3.2.11) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
  activesupport (3.2.11) lib/active_support/callbacks.rb:447:in `_run__4160102059982529417__process_action__1687296135628327387__callbacks'
  activesupport (3.2.11) lib/active_support/callbacks.rb:405:in `__run_callback'
  activesupport (3.2.11) lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks'
  activesupport (3.2.11) lib/active_support/callbacks.rb:81:in `run_callbacks'
  actionpack (3.2.11) lib/abstract_controller/callbacks.rb:17:in `process_action'
  actionpack (3.2.11) lib/action_controller/metal/rescue.rb:29:in `process_action'
  actionpack (3.2.11) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
  activesupport (3.2.11) lib/active_support/notifications.rb:123:in `block in instrument'
  activesupport (3.2.11) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  activesupport (3.2.11) lib/active_support/notifications.rb:123:in `instrument'
  actionpack (3.2.11) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
  actionpack (3.2.11) lib/action_controller/metal/params_wrapper.rb:207:in `process_action'
  activerecord (3.2.11) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
  newrelic_rpm (3.5.5.38) lib/new_relic/agent/instrumentation/rails3/action_controller.rb:34:in `block in process_action'
  newrelic_rpm (3.5.5.38) lib/new_relic/agent/instrumentation/controller_instrumentation.rb:268:in `block in perform_action_with_newrelic_trace'
  newrelic_rpm (3.5.5.38) lib/new_relic/agent/method_tracer.rb:240:in `trace_execution_scoped'
  newrelic_rpm (3.5.5.38) lib/new_relic/agent/instrumentation/controller_instrumentation.rb:263:in `perform_action_with_newrelic_trace'
  newrelic_rpm (3.5.5.38) lib/new_relic/agent/instrumentation/rails3/action_controller.rb:33:in `process_action'
  actionpack (3.2.11) lib/abstract_controller/base.rb:121:in `process'
  actionpack (3.2.11) lib/abstract_controller/rendering.rb:45:in `process'
  actionpack (3.2.11) lib/action_controller/metal.rb:203:in `dispatch'
  actionpack (3.2.11) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
  actionpack (3.2.11) lib/action_controller/metal.rb:246:in `block in action'
  actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:73:in `call'
  actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:73:in `dispatch'
  actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:36:in `call'
  actionpack (3.2.11) lib/action_dispatch/routing/mapper.rb:42:in `call'
  journey (1.0.4) lib/journey/router.rb:68:in `block in call'
  journey (1.0.4) lib/journey/router.rb:56:in `each'
  journey (1.0.4) lib/journey/router.rb:56:in `call'
  actionpack (3.2.11) lib/action_dispatch/routing/route_set.rb:601:in `call'
  rack-pjax (0.7.0) lib/rack/pjax.rb:12:in `call'
  newrelic_rpm (3.5.5.38) lib/new_relic/rack/error_collector.rb:8:in `call'
  newrelic_rpm (3.5.5.38) lib/new_relic/rack/browser_monitoring.rb:12:in `call'
  newrelic_rpm (3.5.5.38) lib/new_relic/rack/developer_mode.rb:24:in `call'
  warden (1.2.1) lib/warden/manager.rb:35:in `block in call'
  warden (1.2.1) lib/warden/manager.rb:34:in `catch'
  warden (1.2.1) lib/warden/manager.rb:34:in `call'
  actionpack (3.2.11) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
  rack (1.4.5) lib/rack/etag.rb:23:in `call'
  rack (1.4.5) lib/rack/conditionalget.rb:25:in `call'
  actionpack (3.2.11) lib/action_dispatch/middleware/head.rb:14:in `call'
  remotipart (1.0.5) lib/remotipart/middleware.rb:30:in `call'
  actionpack (3.2.11) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
  actionpack (3.2.11) lib/action_dispatch/middleware/flash.rb:242:in `call'
  rack (1.4.5) lib/rack/session/abstract/id.rb:210:in `context'
  rack (1.4.5) lib/rack/session/abstract/id.rb:205:in `call'
  actionpack (3.2.11) lib/action_dispatch/middleware/cookies.rb:341:in `call'
  activerecord (3.2.11) lib/active_record/query_cache.rb:64:in `call'
  activerecord (3.2.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:479:in `call'
  actionpack (3.2.11) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
  activesupport (3.2.11) lib/active_support/callbacks.rb:405:in `_run__1343605869620971269__call__1397566206717956287__callbacks'
  activesupport (3.2.11) lib/active_support/callbacks.rb:405:in `__run_callback'
  activesupport (3.2.11) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
  activesupport (3.2.11) lib/active_support/callbacks.rb:81:in `run_callbacks'
  actionpack (3.2.11) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (3.2.11) lib/action_dispatch/middleware/reloader.rb:65:in `call'
  actionpack (3.2.11) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
  actionpack (3.2.11) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
  actionpack (3.2.11) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
  railties (3.2.11) lib/rails/rack/logger.rb:32:in `call_app'
  railties (3.2.11) lib/rails/rack/logger.rb:16:in `block in call'
  activesupport (3.2.11) lib/active_support/tagged_logging.rb:22:in `tagged'
  railties (3.2.11) lib/rails/rack/logger.rb:16:in `call'
  actionpack (3.2.11) lib/action_dispatch/middleware/request_id.rb:22:in `call'
  rack (1.4.5) lib/rack/methodoverride.rb:21:in `call'
  rack (1.4.5) lib/rack/runtime.rb:17:in `call'
  activesupport (3.2.11) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
  rack (1.4.5) lib/rack/lock.rb:15:in `call'
  actionpack (3.2.11) lib/action_dispatch/middleware/static.rb:62:in `call'
  railties (3.2.11) lib/rails/engine.rb:479:in `call'
  railties (3.2.11) lib/rails/application.rb:223:in `call'
  rack (1.4.5) lib/rack/content_length.rb:14:in `call'
  railties (3.2.11) lib/rails/rack/log_tailer.rb:17:in `call'
  rack (1.4.5) lib/rack/handler/webrick.rb:59:in `service'
  /Users/Alex/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/webrick/httpserver.rb:138:in `service'
  /Users/Alex/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/webrick/httpserver.rb:94:in `run'
  /Users/Alex/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/webrick/server.rb:295:in `block in start_thread'

Answer 1

The other answers are correct in general. This exception in particular is caused by an incompatibility between older versions of the newrelic_rpm gem and Ruby 2.0. See rails #8885.

Update the newrelic_rpm gem and it should go away.

Answer 2

You're calling .empty? on a variable that hasn't been initialized somewhere in your detail_args_for method. It's probably to add an additional call to .nil? before checking .empty? if you want to allow Nil values:

if(!someVar.nil? && someVar.empty?)

Answer 3

It is a null reference exception in your method detail_args_for (well technically a Nil reference exception). You are trying to call the method empty? on a variable that has a Nil value, which causes a problem because that isn't defined in nil