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', 'oob3dpoptkhta8kc8ischba940', '216.73.216.167', '1762479890', '1762479890', '/popup_content.php?XTCsid=fee111602053381265bc5ad0a64c84d2&coID=1')

[XT SQL Error]