newModuleTagger: fix case where PR author is ghost

newModuleTagger/find_prs.py

@@ -87,7 +87,7 @@ def find_prs_without_new_module_tag():
             'title': pr['title'],
             'url': "https://github.com/NixOS/nixpkgs/pull/" + str(pr['number']),
             'number': pr['number'],
-            'author': pr['author']['login'],
+            'author': pr['author']['login'] if pr['author'] is not None else '???',
             'files': [file['node'] for file in pr['files']['edges']],
             'labels': [label['node']['name'] for label in pr['labels']['edges']],
         } for pr in prs]