JSON custom field with default value `{}` is set as `null`

[lucagubler]

Deployment Type

Self-hosted

NetBox Version

v4.3.7

Python Version

3.12

Steps to Reproduce

1. Create a new custom field test_config of type JSON with default value {} (empty dict) and assign it to virtual machines.
2. Create a new virtual machine but leave the test_config custom field blank.
3. Virtual machine is created, but test_config is set to null instead of empty dict {}

Expected Behavior

The default value should be set to an empty dict {} instead of null

Observed Behavior

The default value was set to null