Fixing various issues with MUON1 DAOD format
This MR fixes three issues in MUON1:
- no name given to the MCTruthClassifier in the MuonTruthClassifierFallback tool
- incorrect (actually missing) field in the ReadHandle for the input truth collection
- handle the case when there is no pile-up events in the AOD file
MUON1 is not in current use and so this MR has no impact on any ongoing production.
Edited by James Catmore