Dose not allow to close or complete purchase order

[newuser990]

While receiving quantity for some purchase order, if qty is nil and we wish to close the PO by selecting "completed", it does not allow with nil values. For example if Purchase Order quantity was 100. We have received 90 units already. Now supplier says he cannot supply balance 10. We have to close PO by selecting "completed" with qty received as 0 this time, but it does not allow.