Hide variable chooser if current edit widget is hidden

Change-Id: I4b908fd76602170a186b9e1430c7d0e65046d17d
Task-number: QTCREATORBUG-13355
Reviewed-by: Robert Loehning <robert.loehning@theqtcompany.com>
Reviewed-by: hjk <hjk121@nokiamail.com>