examples/certinfo.c: fix compiler warning

    res = curl_easy_perform(curl);

    if(!res) {

      struct curl_certinfo *ci = NULL;

      union {

        struct curl_slist    *to_info;

        struct curl_certinfo *to_certinfo;

      } ptr;

      res = curl_easy_getinfo(curl, CURLINFO_CERTINFO, &ci);

      ptr.to_info = NULL;

      if(!res && ci) {

      res = curl_easy_getinfo(curl, CURLINFO_CERTINFO, &ptr.to_info);

      if(!res && ptr.to_info) {

        int i;

        printf("%d certs!\n", ci->num_of_certs);

        for(i=0; i<ci->num_of_certs; i++) {

        printf("%d certs!\n", ptr.to_certinfo->num_of_certs);

        for(i = 0; i < ptr.to_certinfo->num_of_certs; i++) {

          struct curl_slist *slist;

          for(slist = ci->certinfo[i]; slist; slist = slist->next)

          for(slist = ptr.to_certinfo->certinfo[i]; slist; slist = slist->next)

            printf("%s\n", slist->data);

        }

    }

    curl_easy_cleanup(curl);

  }