merge from trunk fix 48271 for fixing parameters only on lower or upper side
(see http://root.cern.ch/viewvc?view=rev&revision=48271 )


git-svn-id: https://root.cern.ch/svn/root/branches/v5-34-00-patches@48272 27541ba8-7e3a-0410-8455-c3a389f83636