Example with the attached file, if submitted as a changset comment, it will crash.

As a workaround, you might want to extract the comment from the DB and remove the comment.
Given that the changeset comment that lead to issue was 45207:

select body from tracker_changeset_comment where id = 45207 INTO DUMPFILE "/tmp/val";
update tracker_changeset_comment set body = "... truncated ..." where id IN = 45207;

and you can attach val to the artifact as a file attachement