Possible ClassCastException when deleting a document

As usual, the problem is that Hibernate keep the old classes when an extension is upgraded/uninstalled on root namespace (which reload all extensions classes).

For now, I will just make sure that no code in Replication manipulate the class registered in Hibernate, but the ideal fix would be XWIKI-19932 (make sure Hibernate is fully reloaded when on of the registered classes is re-created, but that's unfortunately more complex that it sounds...).