Fix gtf bug -- empty string id fields not handled properly
Fix gtf bug -- empty string id fields not handled properly

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