Fix crash in previous algo

tournaments/models/tournament.py

@@ -196,9 +196,16 @@ class Tournament(models.Model):
             matches.extend(group_stage.match_set.all())
         return matches
 
+    def group_stage_matches(self):
+        matches = []
+        for group_stage in self.groupstage_set.all():
+            matches.extend(group_stage.match_set.all())
+        return matches
+
     def group_stages_running(self):
         if len(self.groupstage_set.all()) > 0:
-            running_group_stage_matches = Match.objects.filter(group_stage__is_null=False, end_date=None)
+            matches = self.group_stage_matches()
+            running_group_stage_matches = [m for m in matches if m.end_date is None]
             return len(running_group_stage_matches) > 0
         else:
             return False