Fix possible NPE exception for bams with no read groups
Fix possible NPE exception for bams with no read groups

itenente/igv,amwenger/igv,itenente/igv,igvteam/igv,godotgildor/igv,igvteam/igv,amwenger/igv,igvteam/igv,amwenger/igv,godotgildor/igv,igvteam/igv,amwenger/igv,amwenger/igv,itenente/igv,itenente/igv,igvteam/igv,godotgildor/igv,godotgildor/igv,itenente/igv,godotgildor/igv