MasterPress 1.3.1 is a compatibility release for PHP 8 and WordPress 5.7. It still remains backwards compatible with older PHP versions.
MPFT_RelatedPostType :: offsetExists( Integer $index )
Checks if the numerical array offset exists in the post types selected in the UI. Since this overrides offset-exists the offset test can be made by calling isset directly on the field object.
Note: This method is intended for internal use and should not be called directly.