Closes #17577: Reference ModelState when determining whether an object is being created

netbox/virtualization/models/clusters.py

@@ -134,7 +134,7 @@ class Cluster(ContactsMixin, PrimaryModel):
         super().clean()
 
         # If the Cluster is assigned to a Site, verify that all host Devices belong to that Site.
-        if self.pk and self.site:
+        if not self._state.adding and self.site:
             if nonsite_devices := Device.objects.filter(cluster=self).exclude(site=self.site).count():
                 raise ValidationError({
                     'site': _(

netbox/virtualization/models/virtualmachines.py

@@ -205,7 +205,7 @@ class VirtualMachine(ContactsMixin, ImageAttachmentsMixin, RenderConfigMixin, Co
             })
 
         # Validate aggregate disk size
-        if self.pk:
+        if not self._state.adding:
             total_disk = self.virtualdisks.aggregate(Sum('size', default=0))['size__sum']
             if total_disk and self.disk is None:
                 self.disk = total_disk