PHP 8.3 compatible

[SerBep]

FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught ValueError: strpos(): Argument #3 ($offset) must be contained in argument #1 ($haystack) in */core/components/simplesearch/model/simplesearch/simplesearch.class.php:437

[halftrainedharry]

This repository is no longer actively maintained.
Use https://github.com/modxcms/SimpleSearch instead.

Also, this issue is a duplicate of modxcms#57