fix(metrics): shiftregister_helpers_required returns None on fresh instance

shiftregister/metrics/views.py

@@ -105,7 +105,8 @@ def metrics(request):
                                 default=F("required_helpers"),
                             )
                         )
-                        .aggregate(sum=Sum("real_required_helpers"))["sum"],
+                        .aggregate(sum=Sum("real_required_helpers"))["sum"]
+                        or 0,
                     ),
                     (
                         "messages_sent_total",