bcftools norm crashes with combination of --atomize and -m -indels

`bcftools norm --fasta-ref test/norm.fa --atomize -m -indels --output-type v test/norm.split.vcf` writes the header, then segfaults.

I can reproduce this all the way back to 1.20. Version 1.19 is unaffected and I think all other combinations of --atomize and -m are working in all versions. 