fixed a bug that caused a segmentation fault when the input BAM has contigs of length 0.
fixed a bug that caused a segmentation fault when the input BAM has contigs of length 0.

EichlerLab/pacbio_variant_caller,EichlerLab/pacbio_variant_caller,EichlerLab/pacbio_variant_caller,EichlerLab/pacbio_variant_caller,EichlerLab/pacbio_variant_caller