Backtrace when adding an invalid IP address with ENFORCE_GLOBAL_UNIQUE

[candlerb]

This is with netbox 1.8.1

• Set ENFORCE_GLOBAL_UNIQUE to True
• Go to page to add a new IP address: /ipam/ip-addresses/add/
• Enter an invalid or incomplete address e.g. 1.2.3 or 1.2.3.4 (not 1.2.3.4/32)
• Click "Add"

Instead of a data validation error, I get an exception:

'unicode' object has no attribute 'ip'

With DEBUG=True, I get a backtrace which ends at:

...
/usr/local/lib/python2.7/dist-packages/django/forms/models.py in _post_clean
            self.instance.full_clean(exclude=exclude, validate_unique=False) ...
> Local vars
/usr/local/lib/python2.7/dist-packages/django/db/models/base.py in full_clean
            self.clean() ...
> Local vars
/opt/netbox/netbox/ipam/models.py in clean
            duplicate_ips = IPAddress.objects.filter(vrf=None, address__net_host=str(self.address.ip))\ ...
> Local vars
  Variable    Value
  self        <IPAddress: >