Line 106 is the gsub on subsequentAuthorSubstitute (however inherited). (EDIT: fixed my reference after a check to the code)
Which CSL file(s) are you using?

Actually, MLA and Chicago have subsequent-author-substitute (which are the ones I mostly used, or derivatives of thereof)... but not a bunch of other styles that don't do author substitution. And CSL 1.0.2 implies the field is optional indeed ("If set..." -- I visibly overlooked it ^^)

So the code lacks a little condition check there indeed. Should be easy to fix, just an "if" around that block. ^^

(Still, let me know which style you primarily target, and I'll do some extra tests upon my return from X-mas vacations)

Now, after a new attempt, I've found that with this one it at least generates the PDF, even though the command \printbibliography still doesn't work, while \csl:reference does

Those that don't work are (for now):

• Ipea ABNT
• UFAL ABNT

Thanks. I'll test those styles upon my return from vacations (on my 2700 reference biblio), just to ensure there are no further unnoticed issues that the one mentioned above. If this is urgent, of course, feel free to experiment. I did test various MLA and Chicago derivatives, and a few European journals, but one never knows, a train can hide another :).

BTW, Ipea ABNT does have a subsequent-author-substitute attribute in the <bibliography> element, so if it fails, it might be another problem. Don't hesitate checking the logs and report it separately if confirmed to be on a different element...

(UFAL ABNT doesn't have the subsequent-author-substitute attribute, so is clearly failing here due at least to it)