Maybe fix Shell crash on exit on MacCatalyst

Check whether ShellSectionRootRenderer has been disposed before
responding to TraitCollectionDidChange to potentially avoid an
ObjectDisposedException retrieving the IApplication service.

Fixes: #33352

Author: jeremy-visionaid

src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellSectionRootRenderer.cs

@@ -143,11 +143,14 @@ public override void ViewSafeAreaInsetsDidChange()
 
 		public override void TraitCollectionDidChange(UITraitCollection previousTraitCollection)
 		{
+			if (_isDisposed)
+				return;
+
 #pragma warning disable CA1422 // Validate platform compatibility
 			base.TraitCollectionDidChange(previousTraitCollection);
 #pragma warning restore CA1422 // Validate platform compatibility
 
-			var application = _shellContext?.Shell?.FindMauiContext().Services.GetService<IApplication>();
+			var application = _shellContext?.Shell?.FindMauiContext()?.Services.GetService<IApplication>();
 			application?.ThemeChanged();
 		}