PO Module - Unstock a Product when it is In Stock

Currently you cannot unstock a product that is in stock back to a supplier if there has been any movement of the product, even if it is showing as in stock and available. This is hugely frustrating especially if the product movement is just to a bin in the warehouse or has been returned to us from the customer. 
 

Please fix the system to allow an unstock of product that is in stock and available.