Fatal error on glossary page

The page that contains the [tooltip_glossary] shortcode used to work fine quite some time, but now (WordPress 6.7.2, Tooltipy 5.5) it creates a fatal error (in the frontend as well as when I try to edit that page).

PHP Fatal error: Uncaught TypeError: array_key_exists(): Argument #2 ($array) must be of type array, true given in /home/username/public_html/www.example.com/wp-content/plugins/bluet-keywords-tooltip-generator/glossary-shortcode.php:20