Fixes refinery#1359 by defaulting --heroku to a blank string instead …

…of a nil which on some systems was putting 'heroku' instead.

core/lib/generators/refinery/cms/cms_generator.rb

@@ -6,7 +6,7 @@ class CmsGenerator < Rails::Generators::Base
                            :desc => "Update an existing Refinery CMS based application"
     class_option :fresh_installation, :type => :boolean, :aliases => nil, :group => :runtime, :default => false,
                            :desc => "Allow Refinery to remove default Rails files in a fresh installation"
-    class_option :heroku,  :type => :string, :default => nil, :group => :runtime, :banner => 'APP_NAME',
+    class_option :heroku,  :type => :string, :default => '', :group => :runtime, :banner => 'APP_NAME',
                            :desc => "Deploy to Heroku after the generator has run."
     class_option :stack,   :type => :string, :default => 'cedar', :group => :runtime,
                            :desc => "Specify which Heroku stack you want to use. Requires --heroku option to function."