Masterpress 1.3.6 is a compatibility release. It resolves an edge case with shared fieldsets not working for MySQL 8 when the fieldset is limited to more than 1 post type or taxonomy or excluding any post types or taxonomies.
MEOW_Field :: offsetExists( Mixed $offset )
An implementation of the offsetExists method in PHP’s ArrayAccess interface. Allows the isset method to be called directly on an array-style offset access to this object (see example). This is not intended to be called directly. Note that this method first checks of the type delegate object supports this method, and if not, will then treat this as a property access on the field.