Fixed a rare crash if still subscribed to items PropertyChanged event and it gets triggered

Microsoft.Toolkit.Uwp.UI/AdvancedCollectionView/AdvancedCollectionView.cs

@@ -469,6 +469,12 @@ namespace Microsoft.Toolkit.Uwp.UI
             {
                 var oldIndex = _view.IndexOf(item);
 
+                // Check if item is in view:
+                if (oldIndex < 0)
+                {
+                    return;
+                }
+
                 _view.RemoveAt(oldIndex);
                 var targetIndex = _view.BinarySearch(item, this);
                 if (targetIndex < 0)