find request on history_instance.thread instead

Author: kseever

docs/advanced.rst

@@ -391,9 +391,8 @@ source model. This is possible by combining the ``bases`` functionality with the
 
     # define your signal handler/callback anywhere outside of models.py
     def add_history_ip_address(sender, **kwargs):
-        instance = kwargs['instance']
         history_instance = kwargs['history_instance']
-        history_instance.ip_address = instance.request.META['REMOTE_ADDR']
+        history_instance.ip_address = history_instance.request.META['REMOTE_ADDR']
 
 
 .. code-block:: python