dijet mass unfolding broken

Since https://gitlab.cern.ch/DasAnalysisSystem/Core/-/merge_requests/107, the unfolding has stopped working:

• a break segmentation happens whenever calling getUnfHist with DijetMass::MjjYmax among the observables (it is related to the use of TUnfoldBinning as a plain type rather than via a pointer);
• the closure fails at the end of running getUnfHist, and the miss rate seems excessively large.