Code Quality: Fixed issue where LastOpenedFlyout was not garbage collected (#14283)

Author: hishitetsu

src/Files.App/App.xaml.cs

@@ -18,9 +18,20 @@ namespace Files.App
 	public partial class App : Application
 	{
 		public static TaskCompletionSource? SplashScreenLoadingTCS { get; private set; }
-		public static CommandBarFlyout? LastOpenedFlyout { get; set; }
 		public static string? OutputPath { get; set; }
 
+		private static CommandBarFlyout? _LastOpenedFlyout;
+		public static CommandBarFlyout? LastOpenedFlyout
+		{
+			set
+			{
+				_LastOpenedFlyout = value;
+
+				if (_LastOpenedFlyout is not null)
+					_LastOpenedFlyout.Closed += LastOpenedFlyout_Closed;
+			}
+		}
+
 		// TODO: Replace with DI
 		public static QuickAccessManager QuickAccessManager { get; private set; } = null!;
 		public static StorageHistoryWrapper HistoryWrapper { get; private set; } = null!;
@@ -137,11 +148,11 @@ private async void Window_Closed(object sender, WindowEventArgs args)
 			StatusCenterViewModel statusCenterViewModel = Ioc.Default.GetRequiredService<StatusCenterViewModel>();
 
 			// A Workaround for the crash (#10110)
-			if (LastOpenedFlyout?.IsOpen ?? false)
+			if (_LastOpenedFlyout?.IsOpen ?? false)
 			{
 				args.Handled = true;
-				LastOpenedFlyout.Closed += (sender, e) => App.Current.Exit();
-				LastOpenedFlyout.Hide();
+				_LastOpenedFlyout.Closed += (sender, e) => App.Current.Exit();
+				_LastOpenedFlyout.Hide();
 				return;
 			}
 
@@ -225,5 +236,15 @@ await SafetyExtensions.IgnoreExceptions(async () =>
 			// Wait for ongoing file operations
 			FileOperationsHelpers.WaitForCompletion();
 		}
+
+		private static void LastOpenedFlyout_Closed(object? sender, object e)
+		{
+			if (sender is not CommandBarFlyout commandBarFlyout)
+				return;
+
+			commandBarFlyout.Closed -= LastOpenedFlyout_Closed;
+			if (_LastOpenedFlyout == commandBarFlyout)
+				_LastOpenedFlyout = null;
+		}
 	}
 }