Returns the tab view item for the specified child view controller.
- macOS 10.10+
The child view controller whose tab view item you want.
The tab view item associated with the view controller or
nil if the view controller is not managed by the tab view controller.
This method is a convenient way to map a tab view item to a newly added child view controller. When you add child view controllers using the
add method, the tab view automatically controller creates a new tab view item. Use this method to fetch that tab view item and configure it.