RT3682: Avoid double-free on OCSP parse error

Found by Kurt Cancemi

(Manual cherry-pick of f8e427154bbc0c33f29fa7aad001b1b655e5995b)
Reviewed-by: Matt Caswell <matt@openssl.org>

apps/ocsp.c

@@ -209,6 +209,7 @@ int MAIN(int argc, char **argv)
                 OPENSSL_free(tport);
             if (tpath)
                 OPENSSL_free(tpath);
+            thost = tport = tpath = NULL;
             if (args[1]) {
                 args++;
                 if (!OCSP_parse_url(*args, &host, &port, &path, &use_ssl)) {