DetachableTabPane doesn't remove area/close stage if last tab is closed

[Former user]

When the last tab in a pane gets dragged out it checks to see if the pane is empty and removes the area or closes the stage as necessary. However, if the last tab is closed by user (or removed programmatically) this does not occur, leaving the empty area or stage.

[Amrullah]

Fixed by commit b670e78