Move more input checker methods to AdminWindow

Elwig/App.xaml.cs

@@ -46,7 +46,7 @@ namespace Elwig {
 
         protected void OnPrintingReadyChanged(EventArgs evt) {
             foreach (Window w in Windows) {
-                foreach (var b in Utils.FindVisualChilds<Button>(w).Where(b => "Print".Equals(b.Tag))) {
+                foreach (var b in Utils.FindAllChildren<Button>(w).Where(b => "Print".Equals(b.Tag))) {
                     b.IsEnabled = IsPrintingReady;
                 }
             }