Use the callback parameter passed to EditEvent.__init__ by passing it…

… to EditPrimary.__init__.

This ensures self.callback is initialised as the calling code expects

gramps/gui/editors/editevent.py

@@ -74,7 +74,7 @@ def __init__(self, dbstate, uistate, track, event, callback=None):
 
         EditPrimary.__init__(self, dbstate, uistate, track,
                              event, dbstate.db.get_event_from_handle,
-                             dbstate.db.get_event_from_gramps_id)
+                             dbstate.db.get_event_from_gramps_id, callback)
 
         self._init_event()