SSL_CTX_get0_certificate() returns NULL if no certificate is installed.
While this should not be the case here due to the loop in
openssl_debug_dump_certificate_chains() proceeding only if the
SSL_CTX_set_current_cert() returns success, it is safer to make
openssl_debug_dump_certificate() explicitly check against NULL before
trying to dump details about the certificate.
Signed-off-by: Pooventhiran G <pooventh@codeaurora.org>