FIX: dav_events: empty some more fields when copy old event.

dav_events/views/events.py

@@ -612,8 +612,10 @@ class EventCreateView(EventPermissionMixin, generic.FormView):
 
             for field in ('id',
                           'owner', 'created_at',
-                          'number',
-                          'planned_publication_date', 'internal_note',):
+                          'number', 'charge',
+                          'registration_howto', 'registration_closed',
+                          'planned_publication_date', 'internal_note',
+                          ):
                 if hasattr(event, field):
                     setattr(event, field, None)