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', '1lh14iq1osoocde2afki56ovl5', '216.73.216.121', '1761838165', '1761838165', '/shop_content.php?XTCsid=304b92a786ebd867b9c51e0edd8808e1&coID=3')

[XT SQL Error]