From Philippe:

This patch insure that ReadBufferSTL and WriteBufferSTL are symetrical in
regard to empty collection (the reading was incorrect).  This solves the
problem describe at

http://root.cern.ch/phpBB2/viewtopic.php?t=1437&highlight=&sid=4c28f9c455a5b
48ac9f9175ac838edf41


git-svn-id: http://root.cern.ch/svn/root/trunk@11189 27541ba8-7e3a-0410-8455-c3a389f83636