Properly handle user profiles without names

If user is mentioned only as co-author in commit and has no
other contribution, nor registered at Launchpad then a profile
is created with empty name. Since the name is required across
the code, use user_id instead of it.

Change-Id: I87bb9cf186d05a6f1299f3150306dcbc01b02fdc

stackalytics/dashboard/web.py

@@ -453,7 +453,7 @@ def get_users_json(record_ids, **kwargs):
     result = []
     for user_id in user_ids:
         user = vault.get_user_from_runtime_storage(user_id)
-        r = {'id': user_id, 'text': user['user_name']}
+        r = {'id': user_id, 'text': user.get('user_name') or user['user_id']}
 
         add_flag = not core_in
         if core_in and user.get('core'):