handle null record when db is bed6+. affected -wao, -loj, closest.
handle null record when db is bed6+. affected -wao, -loj, closest.

arq5x/bedtools2,jmarshall/bedtools2,jmarshall/bedtools2,arq5x/bedtools2,jmarshall/bedtools2,arq5x/bedtools2,jmarshall/bedtools2,jmarshall/bedtools2,arq5x/bedtools2,arq5x/bedtools2