Deprecated Notice on PHP 8.1

Hello,

I just updated one of my sites from PHP 8 to 8.1, and the log is constantly filling with the following 2 notices:

Deprecated: strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated in /home/site/public_html/wp-includes/functions.php on line 7241

Deprecated: str_replace(): Passing null to parameter #3 ($subject) of type array|string is deprecated in /home/site/public_html/wp-includes/functions.php on line 2187

The notices disappear when I deactivate this plugin. Any idea on what is causing this and how to resolve it?

Thanks!
Sarah