Cannot edit IP addresses which have a NAT IP that is assigned to a VM without a cluster

[barnebyte-timewarp]

NetBox version

v3.3.8

Python version

3.8

Steps to Reproduce

1. Assign an IP to an interface of a VM that doesn't have a cluster
   
   

2. Set NAT IP (Inside) of an IP Address to the IP referenced in 1st point
   

3. Try to edit the IP address referenced in 2nd point
   

You get an error:
File "/opt/netbox/netbox/ipam/forms/models.py", line 432, in init
initial['nat_cluster'] = nat_inside_parent.virtual_machine.cluster.pk
AttributeError: 'NoneType' object has no attribute 'pk'

Expected Behavior

The Edit view should be rendered

Observed Behavior

An AttributeError: 'NoneType' object has no attribute 'pk' is raised