Handling of null values when saving related data

The API throws an error when saving a related record with a null value instead of an array of related records.

E.g., Consider I have User and Availability models. A User is related to Availability.

If I make a request, E.g.,

{
  "email": "test@test.com",
  "availability": null,
}

A 500 error is thrown.

We should instead try to unlink all related if sync[availability] is set, or otherwise ignore an empty value.