Postup účastníků - oprava kontroly existence pole

Potřebujeme rozlišovat prázdné pole a None.

mo/web/org_contest.py

@@ -1462,7 +1462,7 @@ def org_contest_advance(ct_id: int):
         for pp in prev_pions:
             # This incurs no real queries as we have all the contests cached
             prev_place_id = sess.query(db.Contest).get(pp.contest_id).place_id
-            if accept_uids and pp.user_id not in accept_uids:
+            if accept_uids is not None and pp.user_id not in accept_uids:
                 reject_by_place_id[prev_place_id] += 1
                 continue
             accept_by_place_id[prev_place_id] += 1