Fix option value parsing in crl2pkcs7 -certfile

Reviewed-by: NRich Saltz <rsalz@openssl.org>

apps/crl2p7.c

@@ -138,7 +138,7 @@ int crl2pkcs7_main(int argc, char **argv)
             if ((certflst == NULL)
                 && (certflst = sk_OPENSSL_STRING_new_null()) == NULL)
                 goto end;
-            if (!sk_OPENSSL_STRING_push(certflst, *(++argv))) {
+            if (!sk_OPENSSL_STRING_push(certflst, opt_arg())) {
                 sk_OPENSSL_STRING_free(certflst);
                 goto end;
             }