free NULL cleanup 5a

Don't check for NULL before calling a free routine.  This gets X509_.*free:
    x509_name_ex_free X509_policy_tree_free X509_VERIFY_PARAM_free
    X509_STORE_free X509_STORE_CTX_free X509_PKEY_free
    X509_OBJECT_free_contents X509_LOOKUP_free X509_INFO_free

Reviewed-by: Richard Levitte <levitte@openssl.org>