How to fix bug 7277966

ERROR
‘Line # 1 Shipment # 1: A document reference exists and the shipment is consigned. The line must be deleted and re-entered without a document reference.’

The line must be deleted and re-entered without a document reference

Steps To Reproduce:
The issue can be reproduced at will with the following steps:
1) Enter and approve a Global Purchase Agreement for a Supplier/Site/Item
2) Setup global ASL for item, set source document with GPA defined, enable "Consigned from Supplier"
3) Create a standard purchase order for the Supplier/Site/Item combination
4) Approve the standard purchase order.
5) Modify the purchase order lines Need By date. A new revision is created. PO requires reapproval.