Deleting a COT that is pointed to be another COT Object field generates CustomObjectType.DoesNotExist on restart

[arthanson]

Plugin Version

0.2.0

NetBox Version

4.4.0

Python Version

3.12

Steps to Reproduce

1. Create a custom object type "cot1"
2. Add a text field f1
3. Create a custom object of this type
4. Create a custom object type "cot2"
5. Add an Object field and for Related object type reference cot1
6. Delete cot1
7. restart NetBox

Expected Behavior

cot1 shouldn't be allowed to be deleted if there are other COTs referencing it.

Observed Behavior

NetBox won't restart with an error "netbox_custom_objects.models.CustomObjectType.DoesNotExist: CustomObjectType matching query does not exist."