"NoMethodError: undefined method `length' for nil:NilClass" when running color_routes

[redbar0n]

My system specs:

OSX 10.9.5
ruby 2.0.0p247 [x86_64-darwin12.3.0]
rails 3.2.12
gem 'color_routes', '1.0.0'
WEBrick 1.3.1
Postgres DB

Cannot run color_routes due to the following "NoMethodError: undefined method `length' for nil:NilClass" error message. Please advise.

› rake color_routes --trace
** Invoke color_routes (first_time)
** Invoke environment (first_time)
** Invoke rails_admin:disable_initializer (first_time)
** Execute rails_admin:disable_initializer
[RailsAdmin] RailsAdmin initialization disabled by default. Pass SKIP_RAILS_ADMIN_INITIALIZER=false if you need it.
** Execute environment
[deprecated] I18n.enforce_available_locales will default to true in the future. If you really want to skip validation of your locale you can set I18n.enforce_available_locales = false to avoid this message.
** Execute color_routes
rake aborted!
NoMethodError: undefined method `length' for nil:NilClass
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/color_routes-1.0.0/lib/color_routes/rails/tasks/color_routes.rake:21:in `block (2 levels) in <top (required)>'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/color_routes-1.0.0/lib/color_routes/rails/tasks/color_routes.rake:21:in `map'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/color_routes-1.0.0/lib/color_routes/rails/tasks/color_routes.rake:21:in `block in <top (required)>'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/task.rb:240:in `call'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/task.rb:240:in `block in execute'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/task.rb:235:in `each'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/task.rb:235:in `execute'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/task.rb:179:in `block in invoke_with_call_chain'
/Users/Magne/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/monitor.rb:211:in `mon_synchronize'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/task.rb:172:in `invoke_with_call_chain'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/task.rb:165:in `invoke'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/application.rb:150:in `invoke_task'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/application.rb:106:in `block (2 levels) in top_level'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/application.rb:106:in `each'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/application.rb:106:in `block in top_level'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/application.rb:115:in `run_with_threads'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/application.rb:100:in `top_level'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/application.rb:78:in `block in run'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/application.rb:176:in `standard_exception_handling'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/application.rb:75:in `run'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/bin/rake:33:in `<top (required)>'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/bin/rake:23:in `load'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/bin/rake:23:in `<main>'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/bin/ruby_executable_hooks:15:in `eval'
/Users/Magne/.rvm/gems/ruby-2.0.0-p247/bin/ruby_executable_hooks:15:in `<main>'
Tasks: TOP => color_routes