fix: System.NullReferenceException when click uploader items

Author: jevonsflash

src/Controls/VUploader.xaml.cs

@@ -141,7 +141,7 @@ private void OnUploadTapped(object sender, TappedEventArgs e)
 
     private void TapGestureRecognizer_Tapped_1(object sender, TappedEventArgs e)
     {
-        var CommandParameter = (sender as Button).BindingContext;
+        var CommandParameter = (sender as VUploader).BindingContext;
         this.Command?.Execute(CommandParameter);
     }
 
@@ -151,7 +151,7 @@ private void RemoveButton_Clicked(object sender, EventArgs e)
         {
             return;
         }
-        var removeCommandParameter = (sender as Button).BindingContext;
+        var removeCommandParameter = (sender as VUploader).BindingContext;
         RemoveCommand?.Execute(removeCommandParameter);
     }
 }