Added an improved guard against trying to fetch milestones for a group value of None.

 - Legacy-Id: 12989

Author: levkowetz

ietf/doc/utils_charter.py

@@ -126,7 +126,7 @@ def historic_milestones_for_charter(charter, rev):
         just_before_next_rev = datetime.datetime.now()
 
     res = []
-    if charter.chartered_group:
+    if hasattr(charter, 'chartered_group'):
         for m in charter.chartered_group.groupmilestone_set.all():
             mh = find_history_active_at(m, just_before_next_rev)
             if mh and mh.state_id == need_state: