Match on undefined attribute.

List, I can't seem to write a simple condition to match on a missing attribute.  I just want to do this:                 if( ! &reply:Filter-Id ) {                         update reply {                                 Vendor-Address-List := foo                         }                 } However, that always returns true, even if Filter-Id isn't returned in the Access-Accept. If I try:                 if( &reply:Filter-Id == "" ) {                         update reply {                                 Vendor-Address-List := foo                         }                 } Then when Filter-Id isn't set, I get: ERROR: Failed retrieving values required to evaluate condition And no match. What is the correct way to match on missing reply attributes? Thanks, schu