Convert spanning deletions called by GATK back to regular indels

Question

[samuelandjw]

GATK calls "" allele (spanning or overlapping deletions), but some of the downstream analysis softwares cannot handle "" allele. Is there a way to convert a record with "*" allele and its preceding record back to one regular indel record?

Using the example provided by GATK website,

I would like to merge the two record at position 14 and 20 in the upper panel to the indel record at position 14 in the lower panel.