ContextWindow: Add HasContextLoaded property

Elwig/Windows/DeliveryScheduleAdminWindow.xaml.cs

@@ -33,10 +33,6 @@ namespace Elwig.Windows {
             ViewModel.FilterOnlyUpcoming = true;
         }
 
-        protected override async Task OnInit(AppDbContext ctx) {
-            LockInputs();
-        }
-
         private async Task RefreshList(bool updateSort = false) {
             var vm = ViewModel;
             var cursor = Mouse.OverrideCursor != null;
@@ -124,15 +120,17 @@ namespace Elwig.Windows {
         }
 
         private async void OnlyUpcomingInput_Changed(object sender, RoutedEventArgs evt) {
+            if (!HasContextLoaded) return;
             await RefreshList();
         }
 
         private async void SearchInput_TextChanged(object sender, TextChangedEventArgs evt) {
+            if (!HasContextLoaded) return;
             await RefreshList(true);
         }
 
         private async void SeasonInput_TextChanged(object sender, TextChangedEventArgs evt) {
-            if (ViewModel.FilterSeason == null) return;
+            if (!HasContextLoaded || ViewModel.FilterSeason == null) return;
             ViewModel.FilterOnlyUpcoming = false;
             await RefreshList();
         }