* Fix - Ensure that when getting costs refunded for an order item there are no PHP errors in sites running PHP 8.0+
* Fix - Improve Background Job Handler compatibility with newer WooCommerce versions while processing a job queue
* Fix - Include products with no costs when sorting products by costs in the products admin screen * Fix - Replace deprecated `is_ajax()` usages in favor of `wp_doing_ajax()` * Misc - Require WooCommerce 3.9.4 or higher