Correcting stock leaves units a buyer is waiting for

Correct stock and deleting a product no longer take units an open checkout is paying for or a paid pre-order is owed.

A negative Correct stock on a product's page takes only units nobody has a claim on. Asking for more is refused, with how many can go and what holds the rest, and nothing moves. Before, it took whatever was on the shelf, so a paid order could find its unit gone.
Deleting a product with units owed to paid pre-orders is refused, the way it already was for units held by an open checkout.