Rails4

I found a bug on Rails 4, after the merge of #196. Basically, when working with an association proxy, sometimes it would create an new object to use for the authorization but that object would then be lingering in the association collection. So, later on the controller or view your association collection would have an unsaved unpopulated object.

This change ensures that the object gets removed after the authorization happen.
And here we make sure it's removed.