Contract contains no cross-plant items

What causes this issue?

You can only define plant conditions for items of
<DS:GLOS. centrally_agreed_contract>centrally agreed contracts</>, i.e.
items for which no plant has been entered.
However, the contract you are processing contains only items with a
plant.

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?

Error message extract from SAP system. Copyright SAP SE.