Use Open dialog instead of Save to resolve interop error

Author: dreamsyntax

source/Reloaded.Mod.Launcher.Lib/Commands/Application/AddApplicationCommand.cs

@@ -169,15 +169,16 @@ private void UpdateIdIfDuplicate(IApplicationConfig config)
     /// </summary>
     private string SelectEXEFile()
     {
-        var dialog = new VistaSaveFileDialog();
-        dialog.OverwritePrompt = false;
+        var dialog = new VistaOpenFileDialog();
         dialog.Title = Resources.AddAppExecutableTitle.Get();
         dialog.Filter = $"{Resources.AddAppExecutableFilter.Get()} (*.exe)|*.exe";
+        dialog.CheckFileExists = true;
+        dialog.Multiselect = false;
 
         if ((bool)dialog.ShowDialog()!)
             return dialog.FileName;
 
-        return "";
+        return string.Empty;
     }
 }