Fix: Fixed ArgumentNullException in AppLifecycleHelper.HandleAppUnhandledException (#15696)

Author: hishitetsu

src/Files.App/Helpers/Application/AppLifecycleHelper.cs

@@ -310,7 +310,7 @@ public static void HandleAppUnhandledException(Exception? ex, bool showToastNoti
 
 			// Save the current tab list in case it was overwriten by another instance
 			SaveSessionTabs();
-			App.Logger.LogError(ex, ex?.Message ?? "An unhandled error occurred.");
+			App.Logger?.LogError(ex, ex?.Message ?? "An unhandled error occurred.");
 
 			if (!showToastNotification)
 				return;