Fix bug in Range::IsEmpty()

Don't update the display implicitly when attaching: want to update display often even if already attached, and this would trigger two updates. Better ask for an update explicitly but once.
When having read input there's no point to update the prompt - the prompt should have been shown already anyway.
This considerably reduces the amounts of re-draws and moves.


git-svn-id: http://root.cern.ch/svn/root/trunk@39860 27541ba8-7e3a-0410-8455-c3a389f83636