Don't throw an exception if a read is unmapped.
Don't throw an exception if a read is unmapped.

alecw/picard,nh13/picard,broadinstitute/picard,alecw/picard,broadinstitute/picard,annkupi/picard,nh13/picard,nh13/picard,alecw/picard,nh13/picard,broadinstitute/picard,alecw/picard,annkupi/picard,broadinstitute/picard,broadinstitute/picard,annkupi/picard,annkupi/picard