Fix initialisation of m_cscSimData handle in MuonSegmentTruthAssociationAlg.cxx
Follows on from !48861 (merged)
This is another trivial config fix for an optional read handle.
This is required to reconstruct Run3 MC in a RAWtoALL workflow, hence is another critical one for the 22.0.56
we'll be needing from the fri, sat or sun nightly.
cc @fwinkl