Fix NPE when doing an index query in which there are no overlapping reads.  Change courtesy of Matt Hanna.
Fix NPE when doing an index query in which there are no overlapping reads.  Change courtesy of Matt Hanna.

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