X509 build_chain(): Fix two potential memory leaks on issuer variable
X509 build_chain(): Fix two potential memory leaks on issuer variable

This also removes an inadequate guard: if (num == ctx->num_untrusted)

Reviewed-by: Tomas Mraz <2bc6038c3dfca09b2da23c8b6da8ba884dc2dcc2@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14422)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl