PHP Fatal error: Uncaught TypeError: unlink()

Wordpress 6, PHP 8.0.x

Internal error 500 during check for positions:

[24-Jun-2022 17:22:44 UTC] PHP Fatal error: Uncaught TypeError: unlink(): Argument #1 ($filename) must be of type string, WP_Error given in /home/wp-content/plugins/ad-inserter/settings.php:5560
Stack trace:
#0 /home/wp-content/plugins/ad-inserter/settings.php(5560): unlink()
#1 /home/wp-content/plugins/ad-inserter/ad-inserter.php(6538): ai_check_page()
#2 /home/wp-includes/class-wp-hook.php(307): ai_ajax_backend()
#3 /home/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters()
#4 /home/wp-includes/plugin.php(476): WP_Hook->do_action()
#5 /home/wp-admin/admin-ajax.php(187): do_action()
#6 {main}
thrown in /home/wp-content/plugins/ad-inserter/settings.php on line 5560