Fix bug due to change of structure for stylesheet

app/models/design/design.rb

@@ -14,7 +14,7 @@ class Design
   has_many :images,as: :imgs, :autosave => true, :dependent => :destroy
   has_many :javascripts, as: :js, :autosave => true, :dependent => :destroy
   has_many :pages
-  has_many :themes, :autosave => true, :dependent => :destroy
+  has_many :themes, as: :css, :autosave => true, :dependent => :destroy
 
   accepts_nested_attributes_for :images, :allow_destroy => true
   accepts_nested_attributes_for :javascripts, :allow_destroy => true

app/models/design/theme.rb

@@ -1,6 +1,6 @@
 class Theme < Stylesheet
   
-  belongs_to :design
+  belongs_to :css, polymorphic: true
   
   protected