WooCommerce Product Bundles 8.3.5

* Fix - Incorrect use of 'WP_Query' with an empty IDs array when editing products, causing performance issues to sites with a large number of products.
* Fix - Failure to invalidate external object cache when calling 'WC_Bundled_Item_Data::save', causing unnecessary database reads/writes on systems using an external object cache.
* Fix - Failure to synchronize the stock status of bundles when changing the stock status/quantity of a bundled product in some edge cases.
* Fix - PHP warning triggered by non-purchasable bundled products with a non-zero minimum quantity.
* Fix - Non-purchasable bundled products are displayed with an "Undefined" bundled product title.
* Tweak - Improved stock sync task runner logging.
* Tweak - Improved handling of non-purchasable bundled products. Introduced '/single-product/bundled-product-unavailable.php' template.

* Fix - Typos in "Group Mode" admin notice text.
* Fix - Invalidate 'bundled_data_items' cache when clearing bundled item stock meta.
* Fix - Escaped attributes in '/templates/single-product/bundled-product-variable.php'.
* Fix - Prevent incorrect display/use of unsupported-type bundled items.
* Fix - Strengthened back-end add-to-cart validation of variable bundled product attributes.
* Tweak - Assign priority to 'Product Data > Bundled Products' tab.
* Tweak - Reduced number of DB queries used to fetch product data when calling 'WC_Product_Bundle::get_bundled_items'.

* Fix - Fatal "return value in write context" error, affecting systems running outdated versions of PHP.