Handle deleted user in the assignee list (#7)

* update condition

* Add comment

---------

Co-authored-by: Kevin Thomas <kevintab@tutanota.com>
Co-authored-by: Sean Lip <sean@seanlip.org>

Author: 3 people

src/github_services.py

@@ -199,6 +199,10 @@ def get_pull_request_dict_with_timestamp(
     """
 
     for assignee in pr_dict['assignees']:
+        if event['assignee'] is None or assignee is None:
+            # This situation can arise if a PR was reviewed by a now-deleted
+            # user.
+            continue
         if event['assignee']['login'] == assignee['login']:
             assignee['created_at'] = parser.parse(event['created_at'])
     return pr_dict