Don't crash if group has no creator

Fixes hypothesis#8734

Author: seanh

h/jinja_extensions/navbar_data.py

@@ -41,7 +41,9 @@ def navbar_data(request):
                 "name": group.name,
                 "pubid": group.pubid,
                 "relationship": (
-                    "Creator" if group.creator.username == username else None
+                    "Creator"
+                    if group.creator and group.creator.username == username
+                    else None
                 ),
             }
             for group in groups

tests/unit/h/jinja2_extensions/navbar_data_test.py

@@ -50,6 +50,25 @@ def test_it(self, pyramid_request, user):
             "username_url": f"http://example.com/users/{user.username}",
         }
 
+    def test_it_with_a_group_with_no_creator(
+        self, pyramid_request, user, factories, group_list_service
+    ):
+        user.groups = group_list_service.associated_groups.return_value = [
+            factories.Group(creator=None)
+        ]
+        pyramid_request.user = user
+
+        result = navbar_data(pyramid_request)
+
+        assert result["groups_suggestions"] == [
+            {
+                "name": group.name,
+                "pubid": group.pubid,
+                "relationship": None,
+            }
+            for group in user.groups
+        ]
+
     def test_it_with_no_user(self, pyramid_request, group_list_service):
         pyramid_request.user = None
         group_list_service.associated_groups.return_value = []