add checks for null hits in TrackPrinter
add checks for null hits in TrackPrinter


iLCSoft/LCIO,petricm/LCIO,iLCSoft/LCIO,petricm/LCIO,iLCSoft/LCIO,iLCSoft/LCIO,iLCSoft/LCIO,iLCSoft/LCIO,petricm/LCIO,petricm/LCIO,petricm/LCIO,petricm/LCIO