Fix 'Next shifts' when there are 'empty' rooms

shiftregister/team/views.py

@@ -29,13 +29,16 @@ def shift_overview(request):
         .order_by("start_at")
     ]
 
-    # probably can do some distinct/group by stuff but not sure how tih django queries
-    context["next_shifts"] = [
+    # only Postgres supports DISTINCT on specific columns, SQLite does not support aggregates on datetime fields
+    context["next_shifts"] = filter(
+        lambda x: x is not None,
+        (
             Shift.objects.filter(room=room, start_at__gt=timezone.now(), deleted=False)
             .order_by("start_at")
             .first()
             for room in Room.objects.all()
-    ]
+        ),
+    )
 
     return render(request, "shift_overview.html", context)