🐛 Some values may be null in datahub, but are non-null in our models

[MatMoore]

Describe the bug.

https://ministryofjustice.sentry.io/issues/5321294599/?alert_rule_id=15157261&alert_type=issue&notification_uuid=ccc3a005-8ade-4aeb-8b87-c209758db688&project=4507181591101440&referrer=slack

In this case description is None, but we are validating that description is a string.

To Reproduce

No response

Expected Behaviour

Two options

1. We change our model to match datahub
2. Cooerce None values to string when reading from datahub. Anytime we do .get(field, "") on the graphql response we need to make sure we handle any case where the field is set, but set to None

Additional context

No response