Added few tests for Selector in Wasm

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Input/RoutedEvents/RoutedEventsPage.xaml

@@ -29,6 +29,13 @@
 						<StackPanel Margin="0, 40">
 							<ToggleSwitch />
 							<Slider VerticalAlignment="Bottom" Value="0.5" Minimum="-1" Maximum="1.5" StepFrequency="0.1" />
+							<ListView x:Name="list">
+								<ListView.ItemsPanel>
+									<ItemsPanelTemplate>
+										<StackPanel Orientation="Horizontal" />
+									</ItemsPanelTemplate>
+								</ListView.ItemsPanel>
+							</ListView>
 						</StackPanel>
 					</Grid>
 				</ScrollViewer>

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Input/RoutedEvents/RoutedEventsPage.xaml.cs

@@ -1,5 +1,6 @@
 using System;
 using Uno.UI.Samples.Controls;
+using Windows.UI;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
 using Windows.UI.Xaml.Input;
@@ -21,6 +22,11 @@ namespace SamplesApp.Samples.RoutedEvents
 
 			btn.Click += (s, e) => btn.Content = $"{btn.Content}.Clk";
 			btn.Tapped += (s, e) => btn.Content = $"{btn.Content}+T";
+
+			list.Items.Add("A");
+			list.Items.Add("B");
+			list.Items.Add("C");
+			list.Items.Add("D");
 		}
 
 		private void HookEvents(Grid grid, TextBlock textBlock)
@@ -69,18 +75,21 @@ namespace SamplesApp.Samples.RoutedEvents
 
 			grid.PointerExited += (s, e) => textBlock.Text += ">>";
 
+			var blue = new SolidColorBrush(Colors.Blue);
+			var white = new SolidColorBrush(Colors.WhiteSmoke);
+
 			grid.PointerPressed += (s, e) =>
 			{
 				textBlock.Text += "_";
-				grid.BorderBrush = SolidColorBrushHelper.Blue;
+				grid.BorderBrush = blue;
 			};
 			grid.PointerReleased += (s, e) =>
 			{
 				textBlock.Text += "-";
-				grid.BorderBrush = SolidColorBrushHelper.WhiteSmoke;
+				grid.BorderBrush = white;
 			};
 
-			grid.BorderBrush = SolidColorBrushHelper.WhiteSmoke;
+			grid.BorderBrush = white;
 			grid.BorderThickness = new Thickness(3.5);
 
 			grid.GotFocus += (s, e) => textBlock.Text += ".F";

src/Uno.UI/UI/Xaml/Controls/Primitives/Selector.wasm.cs

@@ -14,6 +14,11 @@ namespace Windows.UI.Xaml.Controls.Primitives
 
 		private void UpdateItemSelectedState(object item, bool updateTo)
 		{
+			if (item == null)
+			{
+				return;
+			}
+
 			var container = ContainerFromItem(item);
 			if (container is SelectorItem selectorItem)
 			{