[SM-USERS] delete_move_next plugin: Trying to access array offset on value of type null

[Robert K. <rk...@fo...>]

Running squirrelmail-20220115_0200-SVN.devel.tar.gz on Fedora 35, PHP 8,
the delete_move_next plugin generates this error:

Category: PHP
Message: Trying to access array offset on value of type null
FILE: /usr/share/squirrelmail/plugins/delete_move_next/setup.php
LINE: 187