Bug: Org exporter: broken-link errors can't be debugged with debug-on-error [9.3 (release_9.3 @ /usr/share/emacs/28.0.50/lisp/org/)]

[Dima Kogan <dima@secretsauce.net>]

Hi. I'm using the org included with a very recent emacs built from git.

I have a large project consisting of many .org files that I'm exporting
to html. Somewhere there's a broken link, so when I export the project I
get

  user-error: Unable to resolve link: "figures/blahblahblah.svg"

This doesn't tell me where the problem is, specifically, so to find out
I

  (setq debug-on-error t)

and go again. But something about the org code is preventing the
debugger from triggering on this. That really shouldn't be happening.
This is an error that's causing the export to give up and quit, and the
debugger should come up (when debug-on-error).

Also, it would be nice if the error message reported the source file and
line number of the bad link.

Thanks!
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Emacs  : GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.23, cairo version 1.16.0)
 of 2020-09-29, unofficial emacs-snapshot build: http://emacs.secretsauce.net
Package: Org mode version 9.3 (release_9.3 @ /usr/share/emacs/28.0.50/lisp/org/)