Bug fix for FPE in PFOMonalg
requested to merge atlas-particleflow-software/athena:mhodgkin_fixPFlowMonAlg_Sept2021 into 22.0-mc20
Bug fix to skip neutral particle flow FlowElement with E set to exactly 0. Usage of them causes an FPE and they are not of interest for monitoring (such FE are removed from AOD via thinning).