TareCorrectionDialog: Allow actual tare to be null

Elwig/ViewModels/DeliveryAdminViewModel.cs

@@ -125,7 +125,7 @@ namespace Elwig.ViewModels {
             get => int.TryParse(TareString?.Replace(Utils.GroupSeparator, "").Replace(" kg", ""), out var w) ? w : null;
             set => TareString = value == null ? "-" : $"{value:N0} kg{(TargetTare != null ? "*" : "")}";
         }
-        public int ActualTare;
+        public int? ActualTare;
         public int? TargetTare;
         [ObservableProperty]
         private bool _isManualWeighing;