I suppose this is an unusual scenario but I was doing some tests and created some user accounts that I then deleted. However, in another browser, one of the accounts was still logged in and when I logged out I got the following error message.

I tried to follow the error trace and it looks like maybe the activity logger has a problem if the user doing the action has been deleted?

Fatal error: Uncaught mysqli_sql_exception: Column 'object_id' cannot be null in /var/www/html/piwigo/include/dblayer/functions_mysqli.inc.php:132 Stack trace: #0 /var/www/html/piwigo/include/dblayer/functions_mysqli.inc.php(132): mysqli->query() #1 /var/www/html/piwigo/include/dblayer/functions_mysqli.inc.php(550): pwg_query() #2 /var/www/html/piwigo/include/functions.inc.php(669): mass_inserts() #3 /var/www/html/piwigo/include/functions_user.inc.php(1333): pwg_activity() #4 /var/www/html/piwigo/include/user.inc.php(16): logout_user() #5 /var/www/html/piwigo/include/common.inc.php(202): include('...') #6 /var/www/html/piwigo/index.php(11): include_once('...') #7 {main} thrown in /var/www/html/piwigo/include/dblayer/functions_mysqli.inc.php on line 132

Environment
Piwigo 16.0.0RC2 Check for upgrade
Installed on 6 November 2025, 6 days ago
Operating system: Linux
PHP: 8.4.11 (Show info) [2025-11-12 23:24:16]
MySQL: 11.8.3-MariaDB-0+deb13u1 from Debian [2025-11-12 17:24:16]
Graphics Library: External ImageMagick 7.1.1-43
Cache size 14.93 Mo   calculated 2 days ago Refresh

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