Fix mongoid deeply nested polimorphic

Got the commit from github. The roles and sub_roles save.

app/views/admin/attributes/_attribute_field.html.erb

@@ -3,11 +3,10 @@
   <td class='select_mulitlingual' style='text-align:center'>
     <%= f.check_box :locale %>
   </td>
-	<%= f.fields_for :i18n_variable, (attribute_field.i18n_variable.nil? ? attribute_field.build_i18n_variable : attribute_field.i18n_variable) do |f| %>
+	<%= f.fields_for :i18n_variable, (attribute_field.new_record? ? attribute_field.build_i18n_variable : attribute_field.i18n_variable) do |f| %>
 	  <% @site_valid_locales.each do |locale| %>
 	    <td><%= f.text_field locale, :style => "width:130px" %></td>
 	  <% end %>
-		<%= f.hidden_field :id %>
 	<% end %>
   <td class='select_type'>
     <%= f.select :markup, LIST[:markups], {}, {:style => "width:90px"} %>