Fatal Error when bulk printing invoices

Hello!

If WooCommerce Delivery Notes is active alongside QuickPay, selecting a bulk print action from the orders list triggers a fatal TypeError crash.

The cause: another plugin in the handle_bulk_actions filter chain returns NULL instead of a string. QuickPay’s handler declares a strict string type on its $redirect_url parameter and has no tolerance for NULL, so PHP throws a fatal error and the entire admin page crashes.

We resolved it temporarily by patching OrderActionsController.php to accept a nullable string with a null fallback to empty string — one line change.

This is a defensive coding issue. WordPress does not guarantee that other plugins in a filter chain will return a valid value, so QuickPay’s bulk action handler should be made tolerant of NULL input. Would be great to see this addressed in an upcoming release.