Delivery quantity must be entered for the item

IF &[SWITCH]S4H_DOCU_ON_PREMISE& = 'X'.

What causes this issue?

The delivery quantity must be greater than zero, as defined in
Customizing for the item category of this delivery item.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Enter a quantity greater than zero in delivery processing.
Should this error message appear when you are confirming a WMS transfer
order that you want to close with a quantity of zero, it could be that
the delivery item does not allow a quantity of zero. If necessary, ask
the person responsible for Customizing if this is intentional. If so,
you cannot confirm the transfer order with a quantity of zero.
ENDIF.

Error message extract from SAP system. Copyright SAP SE.