fixed vulnerabilities identified by red4sec.com (#4521)
inline int web_client_api_request_v1_charts(RRDHOST *host, struct web_client *w, char *url) {
    (void)url;

    buffer_flush(w->response.data);
    w->response.data->contenttype = CT_APPLICATION_JSON;
    charts2json(host, w->response.data);
    return 200;
}

inline int web_client_api_request_v1_charts(RRDHOST *host, struct web_client *w, char *url) {
    (void)url;

    buffer_flush(w->response.data);
    w->response.data->contenttype = CT_APPLICATION_JSON;
    charts2json(host, w->response.data);
    return 200;
}
