It turns out that Parser gets empty objects (for .djvu files), which are
then used by tag hook functions defined in
extensions/ProofreadPage/includes/ProofreadPage.php.
This started with significant changes made to
includes/media/DjVuHandler.php from 1.35 to 1.37 and carried on to the
current 1.39. Copying DjVuHandler.php from 1.35 over one in 1.39 lets
Proofread Page to work with .djvu files again. Not an ideal solution.
I'm attaching a diff in case someone would be interested and have any
comments.
Thank you,
Šarūnas Burdulis for
lituapedija.net