undefined method `empty?' for nil em CheckoutController#step2

Started POST "/aplicativos/2/checkout?previous_step=1&step=2" for 189.70.6.102 at 2012-11-26 15:45:30 +0000
Processing by CheckoutController#update as JS
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"81Df4LUtlECk2OJrv+itb87ZIjnLcoyLomBzfIYgWfU=", "space_id"=>"7", "previous_step"=>"1", "step"=>"2", "locale"=>"pt-BR", "app_id"=>"2"}
  Rendered checkout/update.js.erb (1.8ms)
Completed 500 Internal Server Error in 12ms

ActionView::Template::Error (undefined method `empty?' for nil:NilClass):
    23:   $modalNextStep.length && $modalNextStep.modal("hide");
    24: 
    25:   <%# Redireciona para a modal de quando o usuário não possui ambientes. %>
    26:   <% @next_step = 1 if @environments.empty? %>
    27: 
    28:   $('<%= escape_javascript render "step", step: (@next_step - 1), app: @app,
    29:                                   environments: @environments, space: @space,
  app/views/checkout/update.js.erb:26:in `_app_views_checkout_update_js_erb___972256260_101083280'
  app/controllers/checkout_controller.rb:55:in `step_2'
  app/controllers/checkout_controller.rb:28:in `update'

redu / apps

undefined method `empty?' for nil em CheckoutController#step2 #135