Define @emitted_hidden_id if it doesn't exists and reuse it if it does.

actionpack/lib/action_view/helpers/form_helper.rb

@@ -1237,7 +1237,7 @@ def submit(value=nil, options={})
       end
 
       def emitted_hidden_id?
-        @emitted_hidden_id
+        @emitted_hidden_id ||= nil
       end
 
       private