ignored extn does not return a value

index.bs

@@ -3827,6 +3827,7 @@ extension does not otherwise require any result values, it SHOULD be defined as
 output=] result, set to [TRUE] to signify that the extension was understood and processed. Likewise, any [=authenticator
 extension=] that does not otherwise require any result values MUST return a value and SHOULD return a CBOR Boolean
 [=authenticator extension output=] result, set to [TRUE] to signify that the extension was understood and processed.
+Finally, there MUST NOT be any values returned for ignored extensions.
 
 ## Extending request parameters ## {#sctn-extension-request-parameters}