underlying error messages for malformed lines when parsing VCF files are not reported

Parse errors at specific lines in VCF files result in a detailed positional error message, but when problematic lines are encountered jalview reports:

Error processing VCF: Format specifier '%s'
java.util.MissingFormatArgumentException: Format specifier '%s'
at java.base/java.util.Formatter.format(Formatter.java:2672)