Can't assign primary IP when creating new IP address

[blipnet]

NetBox version

v3.5.4

Python version

3.8

Steps to Reproduce

1. Click add new IP address
2. Assign address to an Interface
3. Check "Make this primary IP for device/VM"
4. Click Create button

This is not possible anymore, getting below error message

Expected Behavior

1. Click add new IP address
2. Assign address to an Interface
3. Check "Make this primary IP for device/VM"
4. Click Create button

Observed Behavior

[jeremystretch]

Thank you for opening a bug report. Unfortunately, the information you have provided is not sufficient for someone else to attempt to reproduce the reported behavior. Remember, each bug report must include detailed steps that someone else can follow on a clean, empty NetBox installation to reproduce the exact problem you're experiencing. These instructions should include the creation of any involved objects, any configuration changes, and complete accounting of the actions being taken. Also be sure that your report does not reference data on the public NetBox demo, as that is subject to change at any time by an outside party and cannot be relied upon for bug reports.

[kkthxbye-code]

I can replicate this fine. The fix here is broken:

b64b19a#diff-04bd663083dc2a523d431cef07afcaba54ea042bd1113aabcf88afd3d92de1d3R350

For new objects self.instance will be an empty IPAddress object so it will always fail. It needs a check for self.instance.pk before doing the comparison.

Replication steps if the original were not enough:

1. Create a manufacturer mf
2. Create a site si
3. Create a device role dr
4. Create a device type dt with manufacturer set to mf
5. Create a device d of device type dt on site si
6. Create an interface on the d device named inf of 1000BASE-T (1GE).
7. Create an IP address 9.9.9.9/29 with assignment to interface inf and mark the primary IP field.
8. Save the IP