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', '0rc4taa52p0viq29stijenptt0', '216.73.216.9', '1757957641', '1757957641', '/popup_content.php?XTCsid=07630e5b15e9155d8246af3ee660ca0e&coID=1')

[XT SQL Error]