some hotfixing so locations reports refer to can be deleted

src/c3nav/editor/models/changedobject.py

@@ -291,7 +291,7 @@ class ChangedObject(models.Model):
             related_model = field.related_model
             if related_model._meta.app_label != 'mapdata':
                 continue
-            if related_model.__name__ == 'AccessPermission':
+            if related_model.__name__ in ('AccessPermission', 'Report'):
                 continue
             kwargs = {field.field.name+'__pk': self.obj_pk}
             if self.changeset.wrap_model(related_model).objects.filter(**kwargs).exists():

src/c3nav/mapdata/models/report.py

@@ -70,6 +70,8 @@ class Report(models.Model):
 
     @cached_property
     def location_specific(self):
+        if self.location is None:
+            return None
         return self.location.get_child()
 
     @classmethod