When attach a document to PO line - Error "Field [KEY_REF] is mandatory for Category and requires a value"

When attach a document to no part PO line receive below error. Version: 22R2

1. PO > No Part Lines tab > Add a No pert line  
2. Select the PO line > Click on the fie clip mark on the line > Document > New Document
3. Try to attach a document. > OK > receive below error

“Field [KEY_REF] is mandatory for Category and requires a value.”