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', 'h34t27ecthfa2qblhqqhfi2rv3', '216.73.216.249', '1751518774', '1751518774', '/xtshop/shop_content.php?coID=4')

[XT SQL Error]