PHP 8.1.9 Error: add_submenu_page( null

Hey!

The plugin is adding some sub menu item that leads to PHP notices.

In file wp-content/plugins/gamipress/libraries/ct/includes/class-ct-view.php in line 254 the function add_submenu_page() gets passed a null what should be a string.

I see that it’s an aid to get invisible settings pages.
At least the sub menu item should be added with an empty string to prevent many entries in error logs.

Greetings
derRALF