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

Background of the issue:
I am trying to use WPML plugins, including WPML Media Translation 2.7.5, WPML Multilingual CMS 4.6.15, WPML SEO 2.1.0.1, and WPML String Translation 3.2.18, all on PHP 8.1. In Query Monitor, I get returned a lot of messages about deprecated functions. Please see screenshot for details: الرابط المخفي.

Symptoms:
I am seeing a lot of messages about deprecated functions: "rtrim(): Passing null to parameter #1 ($string) of type string is deprecated".

Questions: