Fix a problem in TBranchClones::GetEntry. In case the number of elements in the array

is 0, one must Clear the TClonesArray. This bug was affecting TChain::Merge in case
a TClonesArray was a member of the merged Trees. (thanks to George A. Heintzelman for
reporting this bug).


git-svn-id: http://root.cern.ch/svn/root/trunk@1146 27541ba8-7e3a-0410-8455-c3a389f83636