Undefined array key “dud_instance_name”

Hi and thank you for your helpful plugin!

I’ve been testing PHP 8 on my site and seeing just how many plugins are complaining. Most of the PHP Warnings are of the type “undefined array key” and Dynamic User Directory is reporting one of these with gusto. The full warning is as follows

PHP Warning: Undefined array key "dud_instance_name" in /home/[....]/wp-content/plugins/dynamic-user-directory/includes/core.php on line 1919