Make null-safe.
Make null-safe.

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