fix crash

tournaments/models/tournament.py

@@ -453,7 +453,7 @@ class Tournament(BaseModel):
                 groups.extend(self.round_match_groups(round, broadcasted, hide_empty_matches=True))
 
         if self.display_group_stages():
-            for round in self.round_set.filter(parent=None, group_stage_loser_bracket=True).all().order_by('index'):
+            for round in self.rounds.filter(parent=None, group_stage_loser_bracket=True).all().order_by('index'):
                 groups.extend(self.round_match_groups(round, broadcasted, hide_empty_matches=True))
 
             group_stages = sorted(self.sorted_group_stages(), key=lambda s: (-s.step, s.index))