Fixes #7756: Fix AttributeError exception when editing an IP address assigned to a FHRPGroup

docs/release-notes/version-3.1.md

@@ -1,3 +1,11 @@
+## v3.1-beta2 (FUTURE)
+
+### Bug Fixes
+
+* [#7756](https://github.com/netbox-community/netbox/issues/7756) - Fix AttributeError exception when editing an IP address assigned to a FHRPGroup
+
+---
+
 ## v3.1-beta1 (2021-11-05)
 
 !!! warning "PostgreSQL 10 Required"

netbox/ipam/forms/models.py

@@ -444,8 +444,8 @@ class IPAddressForm(BootstrapMixin, TenancyForm, CustomFieldModelForm):
 
         # Initialize primary_for_parent if IP address is already assigned
         if self.instance.pk and self.instance.assigned_object:
-            parent = self.instance.assigned_object.parent_object
-            if (
+            parent = getattr(self.instance.assigned_object, 'parent_object', None)
+            if parent and (
                 self.instance.address.version == 4 and parent.primary_ip4_id == self.instance.pk or
                 self.instance.address.version == 6 and parent.primary_ip6_id == self.instance.pk
             ):