Code Quality: Avoid crash when focusing file list after window is closed (#17707)

Co-authored-by: seer-by-sentry[bot] <157164994+seer-by-sentry[bot]@users.noreply.github.com>

Author: seer-by-sentry[bot]

src/Files.App/Views/Layouts/BaseGroupableLayoutPage.cs

@@ -171,10 +171,20 @@ await Task.WhenAll(ParentShellPageInstance.SlimContentPage.SelectedItems.Select(
 
 		protected virtual void ItemManipulationModel_FocusFileListInvoked(object? sender, EventArgs e)
 		{
-			var focusedElement = (FrameworkElement)FocusManager.GetFocusedElement(MainWindow.Instance.Content.XamlRoot);
-			var isFileListFocused = DependencyObjectHelpers.FindParent<ListViewBase>(focusedElement) == ItemsControl;
-			if (!isFileListFocused)
-				ListViewBase.Focus(FocusState.Programmatic);
+			try
+			{
+				if (App.AppModel.IsMainWindowClosed)
+					return;
+
+				var focusedElement = (FrameworkElement)FocusManager.GetFocusedElement(MainWindow.Instance.Content.XamlRoot);
+				var isFileListFocused = DependencyObjectHelpers.FindParent<ListViewBase>(focusedElement) == ItemsControl;
+				if (!isFileListFocused)
+					ListViewBase.Focus(FocusState.Programmatic);
+			}
+			catch
+			{
+				// Handle exception in case the window is closed during the operation
+			}
 		}
 
 		protected virtual void ItemManipulationModel_SelectAllItemsInvoked(object? sender, EventArgs e)

src/Files.App/Views/MainPage.xaml.cs

@@ -171,7 +171,7 @@ public async void MultitaskingControl_CurrentInstanceChanged(object? sender, Cur
 
 			// Focus the content of the selected tab item (this also avoids an issue where the Omnibar sometimes steals the focus)
 			await Task.Delay(100);
-			if (ContentPageContext?.ShellPage?.PaneHolder != null)
+			if (!App.AppModel.IsMainWindowClosed && ContentPageContext?.ShellPage?.PaneHolder != null)
 				ContentPageContext.ShellPage.PaneHolder.FocusActivePane();
 		}