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', '8f129d8c31cebaf0bb75cefdbe1b3d24', '216.73.216.213', '1767378866', '1767378866', '/shop/index.php?XTCsid=041c8fc0413f2441df67fe52a6815a15&cPath=28')

[XT SQL Error]