Fixed: PO receipts with zero accepted units are not handled correctly (OFBIZ-13376)

[golja]

As detailed in OFBIZ-13376, currently, when a PO is received with zero accepted units (e.g., via the ‘ReceiveInventory’ screen), the system creates:

• an inventory item with quantity set to zero
• a receipt with zero accepted units, even when there are no rejected units.

This behavior is not desirable.

When receiving a PO,

• if no item units are accepted, the system should not create an inventory item with zero quantity
• if rejected units are also zero, the system should not create a receipt.

The changes in this PR:

• avoid creating a receipt and an inventory item when both accepted and rejected quantities are zero
• create a receipt, but not an inventory item, when the accepted quantity is zero, but there are rejected units.