rake db:migrateを実行すると以下のようなエラーになります。
どなたか考えられる対処法をお教えいただけないでしょうか。
プログラミング初心者で、いろいろ調べましたがどうにもいかず…

rake aborted!
NoMethodError: undefined method `register_preprocessor' for nil:NilClass
/usr/local/rvm/gems/ruby-2.2.1/gems/i18n-js-3.0.0.rc11/lib/i18n/js/engine.rb:10:in `block in <class:Engine>'
/usr/local/rvm/gems/ruby-2.2.1/gems/railties-4.2.0/lib/rails/initializable.rb:30:in `instance_exec'
/usr/local/rvm/gems/ruby-2.2.1/gems/railties-4.2.0/lib/rails/initializable.rb:30:in `run'
/usr/local/rvm/gems/ruby-2.2.1/gems/railties-4.2.0/lib/rails/initializable.rb:55:in `block in run_initializers'
/usr/local/rvm/gems/ruby-2.2.1/gems/railties-4.2.0/lib/rails/initializable.rb:54:in `run_initializers'
/usr/local/rvm/gems/ruby-2.2.1/gems/railties-4.2.0/lib/rails/application.rb:352:in `initialize!'
/home/ubuntu/workspace/config/environment.rb:5:in `<top (required)>'
/usr/local/rvm/gems/ruby-2.2.1/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `require'
/usr/local/rvm/gems/ruby-2.2.1/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `block in require'
/usr/local/rvm/gems/ruby-2.2.1/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:240:in `load_dependency'
/usr/local/rvm/gems/ruby-2.2.1/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `require'
/usr/local/rvm/gems/ruby-2.2.1/gems/railties-4.2.0/lib/rails/application.rb:328:in `require_environment!'
/usr/local/rvm/gems/ruby-2.2.1/gems/railties-4.2.0/lib/rails/application.rb:443:in `block in run_tasks_blocks'