Error in data referencing

What causes this issue?

Error in data reference.

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?

Please check data assignment in class /FTI/CL_NAMESPACE_VALIDATION ->
VALIDATION_FOR_REPORT( )

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.