Warning message below every single photo after upgrade to PHP 8.1

[Martin6502]

After upgrading my Website from PHP 7.4 to PHP 8.1 running Piwigo 13.3.0 together with Bootstrap Darkroom there is an error message below every single photo within all albums which says:
Warning: Undefined array key "thumbnail_desc" in /www/htdocs/w00bce33/photo/themes/bootstrap_darkroom/include/config.php on line 209

Switching back to PHP 7.4 solves the problem but this PHP version it is out of maintenance now.
I'm happy to help if you need more information.

[Martin6502]

Even if it's not a perfect solution, I've found a workaround by modifying the PHP error_reporting.
Simply change at local\config\config.inc.php:
$conf['show_php_errors'] = '0';

[edison23]

This issue with undefined keys and variables very wide-spread in the theme. I get loads of _data/templates_c/1buv8ho^0ac59ae126c6f9102840db0d8a285c11862ecaf9_0.file.comment_list.tpl.php (...) on line 57 which is coming from themes/bootstrap_darkroom/template/comment_list.tpl.

But! I found out that if you disable comments altogether, no errors are produced. (This also applies to themes modus and stripped_reponsive.

It's not ideal, but it's still more acceptable for me than having two errors per second written to the Apache error logs.

I'm on PHP Version 8.1.2-1ubuntu2.13.

[plegall]

Do you still have the problem nowadays?

[edison23]

Actually, I don't. I just tried activating the comments again and I don't see any error in the photo pages.
I'm on PHP Version 8.1.2-1ubuntu2.14.

[herdivineshadow]

I have this error on Piwigo 14.2.0 and PHP 8.1.25 (Martin6502's error that is, not edison23's)

[EddyLB]

I encountered the same error on Piwigo 13.8, PHP 8.0.30, MySQL: 10.6.16-MariaDB and Bootstrap Darkroom 2.5.17. Maintenance tools did not help but I have fixed the issue by disabling "Social Integration" in the settings of the theme and re-enabling them later. Strange…