Bugfix in copy event feature: load_from_instance() initialized empty

fields.

dav_events/forms/events.py

@@ -897,6 +897,8 @@ class SummaryForm(EventCreateForm):
                                     widget=forms.Textarea(attrs={'rows': 5}))
 
     def proceed_session_data(self, session_data):
+        super(SummaryForm, self).proceed_session_data(session_data)
+
         registration_required = self._session_data.get('registration_required', False)
         if registration_required:
             deadline = self._session_data.get('deadline', None)