Attribute cannot be deleted for BP &1, otherwise evaluation is empty

What causes this issue?

Deletion of this attribute deletes the last attribute for the
evaluation. Empty assignments cannot, however, be saved. For this reason
, the attribute is not deleted. Use the report for deleting assignments
for this business partner.

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?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.