[Resolved] rtrim(): Passing null to parameter #1 ($string) of type string is deprecated

Background of the issue:
I am trying to: This happens on all websites since updating to PHP 8.3. There are several tickets here that have been closed without actually solving the problem.
Deprecated rtrim(): Passing null to parameter #1 ($string) of type string is deprecated wp-includes/formatting.php:2831 rtrim() wp-includes/formatting.php:2831 untrailingslashit() wp-includes/formatting.php:2816 trailingslashit() wp-content/plugins/sitepress-multilingual-cms/classes/url-handling/class-wpml-include-url.php:23 WPML_Include_Url->filter_include_url() wp-includes/class-wp-hook.php:326 apply_filters('script_loader_src') wp-content/plugins/query-monitor/classes/Collector_Assets.php:454 do_action('shutdown') wp-includes/load.php:1270 shutdown_action_hook() wp-includes/load.php:1270 176 Plugin: sitepress-multilingual-cms

Symptoms:
rtrim(): Passing null to parameter #1 ($string) of type string is deprecated

Questions:
You need to fix this bug.