Color of front and rear ports not nullable on bulk edit

[phurrelmann]

NetBox version

V3.3.5

Python version

3.9

Steps to Reproduce

Colors defined on front and rearports are not nullable on bulk edit.

1. Create more than 2 front or rear ports
2. Select 2 or more front or rear ports and do a bulk edit
3. Color can be changed but not cleared

I can prepare a PR, if accepted

Expected Behavior

Color field on bulk edit of front and rear ports should be nullable and the checkbox "Set Null" is visible

Observed Behavior

Color field on bulk edit of front and rear ports are not nullable. The check box "Set Null" is missing