[Openid-specs-ab] What to return when the claim value doesn't exist

[George Fletcher]

Hi,

I just read through the OIDC Core spec and I don't see any guidance on 
what should be returned in either the id_token or from the /userinfo 
endpoint when a specific claim is requested, but the claim value doesn't 
exist.

Is the best practice to just not return the field at all, or return the 
claim field name with an empty value?

Thanks,
George