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', '9t9tb9bvgck4b41avhq68e6ei2', '216.73.216.4', '1771320275', '1771320275', '/product_info.php?XTCsid=cdfc0f2ea8be6cebe1f6056b0a37d83f&info=p12_33-feet-crape-paper.html&language=de')

[XT SQL Error]