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', 'kagt40l722nqvt3pqevr31kg52', '216.73.216.9', '1758097354', '1758097354', '/popup_content.php?XTCsid=502c4d4f7753d1888d9a6ca985d5c9c9&coID=1')

[XT SQL Error]