GroupNavigationItem allows for items to be set both at creation as well as later by modifying the `items` property. When adding (or removing) items, new items are not attached to the parent NavigationBar and removed items are not detached. This prevents RadioButtonNavigationItems from properly being selected when a NavigationBar is told to select the item, and the item's parent may not be the NavigationBar.
<rdar://problem/70619452>