Bug when transcript_id is "0" in input

[julienlag]

Hello,
thanks a lot for this program, I've been using it for several years.
FYI, I've discovered a small bug with an easy fix (line 48). When transcript_id is "0",  the $id && $f[0]; test fails, and the corresponding line is skipped. I fixed it in my local copy by replacing
next unless $id && $f[0];
with
next unless (defined($id) && defined($f[0]));
on line 48.
Best regards