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', 'abhac9usa4i4gf99a66obrltu7', '216.73.216.130', '1760916781', '1760916781', '/shop_content.php?XTCsid=e9d124d75edbd4a3c97ff72681eedadb&coID=3')

[XT SQL Error]