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', '8rhfr4e59rnf5q33vf5unjp0a6', '216.73.216.9', '1758014480', '1758014480', '/popup_content.php?XTCsid=1455d70b156c4853db961f68b595bbe7&coID=1')

[XT SQL Error]