Fix: Fixed possible System.NullReferenceException in ThemeHelper (#12175)

Author: yaira2

src/Files.App/Helpers/ThemeHelper.cs

@@ -17,8 +17,8 @@ namespace Files.App.Helpers
 	public static class ThemeHelper
 	{
 		private const string selectedAppThemeKey = "theme";
-		private static Window currentApplicationWindow;
-		private static AppWindowTitleBar titleBar;
+		private static Window? currentApplicationWindow;
+		private static AppWindowTitleBar? titleBar;
 
 		// Keep reference so it does not get optimized/garbage collected
 		public static UISettings UiSettings;
@@ -49,7 +49,8 @@ public static void Initialize()
 			currentApplicationWindow = App.Window;
 
 			// Set TitleBar background color
-			titleBar = App.GetAppWindow(currentApplicationWindow).TitleBar;
+			if (currentApplicationWindow is not null)
+				titleBar = App.GetAppWindow(currentApplicationWindow).TitleBar;
 
 			// Apply the desired theme based on what is set in the application settings
 			ApplyTheme();
@@ -62,24 +63,19 @@ public static void Initialize()
 		private static async void UiSettings_ColorValuesChanged(UISettings sender, object args)
 		{
 			// Make sure we have a reference to our window so we dispatch a UI change
-			if (currentApplicationWindow is not null)
-			{
-				// Dispatch on UI thread so that we have a current appbar to access and change
-				await currentApplicationWindow.DispatcherQueue.EnqueueAsync(() =>
-				{
-					ApplyTheme();
-				});
-			}
+			if (currentApplicationWindow is null)
+				return;
+
+			// Dispatch on UI thread so that we have a current appbar to access and change
+			await currentApplicationWindow.DispatcherQueue.EnqueueAsync(ApplyTheme);
 		}
 
 		private static void ApplyTheme()
 		{
 			var rootTheme = RootTheme;
 
 			if (App.Window.Content is FrameworkElement rootElement)
-			{
 				rootElement.RequestedTheme = rootTheme;
-			}
 
 			if (titleBar is not null)
 			{

src/Files.App/ViewModels/MainPageViewModel.cs

@@ -276,9 +276,7 @@ public async void OnNavigatedTo(NavigationEventArgs e)
 				return;
 
 			if (drivesViewModel.Drives.Count == 0)
-			{
 				await drivesViewModel.UpdateDrivesAsync();
-			}
 
 			//Initialize the static theme helper to capture a reference to this window
 			//to handle theme changes without restarting the app