1366 - Incorrect integer value: '' for column 'customer_id' at row 1

insert into whos_online (customer_id, full_name, session_id, ip_address, time_entry, time_last_click, last_page_url) values ('', 'Guest', '59q19u22tu9c6p5es77ml8lcp3', '216.73.216.63', '1774478362', '1774478362', '/index.php?XTCsid=e32f172c0b23edb48fc4fb80463cba38')

[XT SQL Error]