[Resolved] PHP 8.1.3 deprecate warnings

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

wp-includes/formatting.php:2809

174 Plugin: sitepress-multilingual-cms
wp-includes/formatting.php:2809
rtrim()
wp-includes/formatting.php:2809
untrailingslashit()
wp-includes/formatting.php:2794
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:310
apply_filters('style_loader_src')
wp-includes/class-wp-styles.php:412
WP_Styles->_css_href()
wp-includes/class-wp-styles.php:221
WP_Styles->do_item()
wp-includes/class-wp-dependencies.php:137
WP_Dependencies->do_items()
wp-includes/script-loader.php:2213
print_admin_styles()
wp-includes/class-wp-hook.php:308
do_action('admin_print_styles')
wp-admin/admin-header.php:132

My site is experiencing a lot of server error. My host says resources are used by a plugin and I'm trying to understand which is the one creating this overload.
this is a message I get from Query Monitor.
almosto all of my PHP errors come from sitepress-multilingual-cms

here you have the debug. Please note thah some of the plugin that are listed as not installed are installed in fact