Fix delete key executing twice on mail list.

Wino.Mail/Views/MailListPage.xaml.cs

@@ -62,6 +62,10 @@ namespace Wino.Views
         {
             base.OnNavigatedFrom(e);
 
+            // Dispose all WinoListView items.
+
+            MailListView.Dispose();
+
             this.Bindings.StopTracking();
 
             RenderingFrame.Navigate(typeof(IdlePage));
@@ -347,16 +351,6 @@ namespace Wino.Views
             SearchBar.PlaceholderText = Translator.SearchBarPlaceholder;
         }
 
-        private void ProcessMailItemKeyboardAccelerator(UIElement sender, ProcessKeyboardAcceleratorEventArgs args)
-        {
-            if (args.Key == Windows.System.VirtualKey.Delete)
-            {
-                args.Handled = true;
-
-                ViewModel?.ExecuteMailOperationCommand?.Execute(MailOperation.SoftDelete);
-            }
-        }
-
         /// <summary>
         /// Thread header is mail info display control and it can be dragged spearately out of ListView.
         /// We need to prepare a drag package for it from the items inside.