update/final: Return error if key is not set

update/final: Return error if key is not set

Also make sure the key is not set if the key
length is changed on the context after the key was
set previously.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22590)