Validate config options during x509 extension creation

Validate config options during x509 extension creation

There are several points during x509 extension creation which rely on
configuration options which may have been incorrectly parsed due to
invalid settings.  Preform a value check for null in those locations to
avoid various crashes/undefined behaviors

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/23183)