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', 'sgeoook4mbrmj4fs7eu2is46b5', '216.73.216.9', '1758190406', '1758190406', '/product_info.php?XTCsid=9265b55633a2cb4e8ed6db3536c73ca5&info=p8_100-Placemats.html&language=de')

[XT SQL Error]