Fix a crash in X509v3_asid_subset()

Fix a crash in X509v3_asid_subset()

If the asnum or rdi fields are NULL and the ASIdentifiers are otherwise
subsets then this will result in a crash. Of note is that rdi will usually
be NULL.

Reported by Theo Buehler (@botovq)

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Yang <kaishen.yy@antfin.com>
Reviewed-by: Todd Short <todd.short@me.com>
(Merged from https://github.com/openssl/openssl/pull/18514)

(cherry picked from commit 01fc9b6bce82f0534d6673659a0e59a71f57ee82)