Fix: Fixed NullReferenceException in Item_Opening (#14699)

Author: yaira2

src/Files.App/UserControls/Menus/FileTagsContextMenu.cs

@@ -1,20 +1,11 @@
 // Copyright (c) 2023 Files Community
 // Licensed under the MIT License. See the LICENSE.
 
-using CommunityToolkit.Mvvm.DependencyInjection;
-using Files.App.Utils;
-using Files.App.Helpers;
-using Files.Core.Services.Settings;
-using Files.Core.ViewModels.FileTags;
-using Files.Shared.Extensions;
+using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Markup;
 using Microsoft.UI.Xaml.Media;
-using System;
-using System.Collections.Generic;
-using System.Linq;
 using static Files.App.Helpers.MenuFlyoutHelper;
-using Microsoft.UI.Xaml;
-using Microsoft.UI.Xaml.Markup;
 
 namespace Files.App.UserControls.Menus
 {
@@ -62,10 +53,13 @@ private void TagItem_Click(object sender, Microsoft.UI.Xaml.RoutedEventArgs e)
 			}
 		}
 
-		private void Item_Opening(object sender, object e)
+		private void Item_Opening(object? sender, object e)
 		{
 			Opening -= Item_Opening;
 
+			if (SelectedItems is null)
+				return;
+
 			// go through each tag and find the common one for all files
 			var commonFileTags = SelectedItems
 				.Select(x => x.FileTags ?? Enumerable.Empty<string>())