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', 'v39lb502krch86c6ac6tbka8d5', '216.73.216.145', '1778402098', '1778402098', '/shop_content.php?XTCsid=1455d70b156c4853db961f68b595bbe7&coID=3')

[XT SQL Error]