Don't crash when not logged in

events/models.py

@@ -36,6 +36,9 @@ class Event(models.Model):
 
 
     def registration_of(self, user):
+        if not user.is_authenticated:
+            return None
+
         registrations = self.eventregistration_set.filter(user=user).all()
         if not registrations:
             return None