Attempt to fix occasional GroupableItemsViewController disposed crash

Author: hartez

Xamarin.Forms.Platform.iOS/CollectionView/ItemsViewController.cs

@@ -66,7 +66,7 @@ protected override void Dispose(bool disposing)
 
 				_emptyUIView?.Dispose();
 				_emptyUIView = null;
-	
+
 				_emptyViewFormsElement = null;
 
 				ItemsViewLayout?.Dispose();