Segfault on empty VCF file in multiallelic filter #50
Description
During some testing in a data analysis pipeline using vafator, I noticed that this tools segfaults when you give it an empty VCF file (i.e., one without any variants but with a metadata header).
The segfault prevents any user from finding out the root cause of the issue, therefore to address this vafator should either raise a proper Exception or error on an empty vcf file or handle the file appropriatly (i.e., write output files not containing anything, possibly with a warning).