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', 'j2pu57o2tkec2volu3je1aobf7', '216.73.216.176', '1762411546', '1762411546', '/popup_content.php?XTCsid=ca28ab8f46bb6e791b42fe9b92719761&coID=1')

[XT SQL Error]