fix: array indexing problem

STranslate/View/MainWindow.xaml.cs

@@ -73,6 +73,7 @@ namespace STranslate.View
         /// <param name="e"></param>
         private void Window_Deactivated(object sender, EventArgs e)
         {
+            if (vm == null) return;
             if (!vm.IsTopmost)
             {
                 vm.Speech.SpeakAsyncCancelAll();

STranslate/ViewModel/MainVM.cs

@@ -22,7 +22,7 @@ namespace STranslate.ViewModel
 
             if (!ReadConfig())
             {
-                Task.Delay(3000);
+                IsVisibility = false;
                 Environment.Exit(-1);
             }