Raise error when subprocess call to variant mapper fails. Before, when read_variant_map.py exited with error the output file was truncated and phASER used this truncated file for further analysis.
Prevent variant mapper from using wrong field for AS. When reads have a different number of fields, the AS field is set using the index from the first read. Now for each read the index position of the AS field is searched, instead of assuming this index position is always the same for all reads.