[PHP8] Uncaught TypeError: array_merge(): Argument #1 must be of type array, bool given in...

Overview of the issue

If you are using WordPress sticky posts in combination with PHP 8, you may might encounter an issue where attempting to save a translation results in an endless spinning icon. The following PHP error will be displayed as well:

Uncaught TypeError: array_merge(): Argument #1 must be of type array, bool given in /sitepress-multilingual-cms/classes/sticky-posts/wpml-sticky-posts-sync.php:69

Workaround

Currently, a direct solution for this specific error is not documented. We recommend users facing this problem to contact WPML assistance for further support and troubleshooting.