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', 'st54h8rk4h5cau5ud7j331def1', '216.73.217.120', '1793248272', '1793248272', '/popup_content.php?XTCsid=80c3e9fc87b53cb0d288d19ef4e9b63c&coID=1')

[XT SQL Error]