Cache behavior assumes browser request includes all Variant'ed headers

[jyasskin]

https://httpwg.org/http-extensions/draft-ietf-httpbis-variants.html#cache says "... For each variant in variants-header ... Let request-value be the field-value(s) associated with field-name in incoming-request." I don't see any handling of the case where there is no field-name header in incoming-request. The algorithms in https://httpwg.org/http-extensions/draft-ietf-httpbis-variants.html#backports then also don't handle the case where request-value is empty.

Sorry if I've just missed where you handle the empty case.