check for empty output in filtered candidates list before attempting to merge output BED.
check for empty output in filtered candidates list before attempting to merge output BED.

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