Minor compatibility changes for newest root version

I noticed that with the current ROOT master branch there were some errors due to this commit which removed some functions that were used by RooExpandedDataHisthttps://github.com/root-project/root/commit/23d861273f56c28a6bad45028115f80228816b6f#diff-5d45ec2a7c3b67ee61c40ea0f837b4cd6a7cae6965f05f603c1d2b6e432ffc18