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', 'ducrtnpuevcobufk72md64td96', '216.73.216.155', '1767600765', '1767600765', '/product_info.php?XTCsid=d163dd0fc0b54bf3066f85422c77e00a&info=p19_10-Paper-Plates.html&language=de')

[XT SQL Error]