Update Nullability

src/CommunityToolkit/Xamarin.CommunityToolkit/Views/TabView/TabView.shared.cs

@@ -518,7 +518,7 @@ namespace Xamarin.CommunityToolkit.UI.Views
 			tabStripContent.Children.Remove(tabViewItem);
 		}
 
-		void AddTabViewItem(TabViewItem tabViewItem, int index = -1)
+		void (TabViewItem tabViewItem, int index = -1)
 		{
 			tabViewItem.PropertyChanged -= OnTabViewItemPropertyChanged;
 			tabViewItem.PropertyChanged += OnTabViewItemPropertyChanged;