我正在尝试通过http://railstutorial.org/自学 Rails 。我昨晚放弃了教程应用程序的工作，然后今天又回来了。现在，当我启动 Spork 服务器时出现错误。这是错误的痕迹。
spork Using RSpec Loading Spork.prefork block... can't convert nil into Hash (TypeError) /usr/local/lib/ruby/gems/1.8/gems/activemodel-3.0.0/lib/active_model/validations/validates.rb:90:in merge' /usr/local/lib/ruby/gems/1.8/gems/activemodel-3.0.0/lib/active_model/validations/validates.rb:90:invalidates' /usr/local/lib/ruby/gems/1.8/gems/activemodel-3.0.0/lib/active_model/validations/validates.rb:83:in each' /usr/local/lib/ruby/gems/1.8/gems/activemodel-3.0.0/lib/active_model/validations/validates.rb:83:invalidates' /Users/chietala/Desktop/rails_projects/sample_app/app/models/user.rb:20 /usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:454:in load' /usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:454:inload_file' /usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:591:in new_constants_in' /usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:453:inload_file' /usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:340:in require_or_load' /usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:300:independ_on' /usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.0/lib/active_support/dependencies.rb:216:in require_dependency' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/engine.rb:138:ineager_load!' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/engine.rb:137:in each' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/engine.rb:137:ineager_load!' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/engine.rb:135:in each' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/engine.rb:135:ineager_load!' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/application.rb:108:in eager_load!' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/application/finisher.rb:41 /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/initializable.rb:25:ininstance_exec' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/initializable.rb:25:in run' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/initializable.rb:50:inrun_initializers' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/initializable.rb:49:in each' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/initializable.rb:49:inrun_initializers' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/application.rb:134:in initialize!' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/application.rb:77:insend' /usr/local/lib/ruby/gems/1.8/gems/railties-3.0.0/lib/rails/application.rb:77:in method_missing' /Users/chietala/Desktop/rails_projects/sample_app/spec/../config/environment.rb:5 /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:ingem_original_require' /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in require' /Users/chietala/Desktop/rails_projects/sample_app/spec/spec_helper.rb:10 /usr/local/lib/ruby/gems/1.8/gems/spork-0.8.4/bin/../lib/spork.rb:23:inprefork' /Users/chietala/Desktop/rails_projects/sample_app/spec/spec_helper.rb:4 /usr/local/lib/ruby/gems/1.8/gems/spork-0.8.4/lib/spork/test_framework.rb:138:in load' /usr/local/lib/ruby/gems/1.8/gems/spork-0.8.4/lib/spork/test_framework.rb:138:inpreload' /usr/local/lib/ruby/gems/1.8/gems/spork-0.8.4/lib/spork/app_framework.rb:64:in preload' /usr/local/lib/ruby/gems/1.8/gems/spork-0.8.4/lib/spork/test_framework.rb:134:inpreload' /usr/local/lib/ruby/gems/1.8/gems/spork-0.8.4/bin/../lib/spork.rb:67:in exec_prefork' /usr/local/lib/ruby/gems/1.8/gems/spork-0.8.4/lib/spork/test_framework.rb:120:inpreload' /usr/local/lib/ruby/gems/1.8/gems/spork-0.8.4/lib/spork/run_strategy/forking.rb:25:in preload' /usr/local/lib/ruby/gems/1.8/gems/spork-0.8.4/bin/../lib/spork/runner.rb:74:inrun' /usr/local/lib/ruby/gems/1.8/gems/spork-0.8.4/bin/../lib/spork/runner.rb:9:in run' /usr/local/lib/ruby/gems/1.8/gems/spork-0.8.4/bin/spork:10 /usr/local/bin/spork:19:inload' /usr/local/bin/spork:19
幸运的是，我使用 Git 进行版本控制，当我收到这个问题时，我在一个单独的分支中，但是切换到 master 仍然会导致错误。
我不确定在哪里或如何解决这个问题。有人有想法么？