AttributeError: 'NoneType' object has no attribute 'is_authenticated'

Thalia Technicie
2020-03-11T23:05:04+01:00

Sentry Issue: [CONCREXIT-2A](https://sentry.io/organizations/thalia/issues/1560438241/?referrer=gitlab_integration)

```
AttributeError: 'NoneType' object has no attribute 'is_authenticated'
(14 additional frame(s) were not displayed)
...
File "rest_framework/serializers.py", line 529, in to_representation
ret[field.field_name] = field.to_representation(attribute)
File "rest_framework/fields.py", line 1905, in to_representation
return method(value)
File "events/api/serializers.py", line 86, in _class_names
if services.is_user_registered(self.context["member"], instance):
File "events/services.py", line 24, in is_user_registered
if not event.registration_required or not member.is_authenticated:
File "django/utils/functional.py", line 225, in inner
return func(self._wrapped, *args)
```