Properly initialise ReadHandleKey for TRT_SegmentsToTrack
Self-explanatory. Fixes following warnings in cosmics reco
SGInputLoader 0 0 WARNING unable to find proxy for ( 'Trk::SegmentCollection' , 'StoreGateSvc+TRTEndcapSegments' )
SGInputLoader 0 0 WARNING unable to find proxy for ( 'Trk::SegmentCollection' , 'StoreGateSvc+TRTBarrelSegments' )
SGInputLoader 0 0 WARNING unable to find proxy for ( 'PRD_MultiTruthCollection' , 'StoreGateSvc+PRD_MultiTruthTRT' )