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', '7bqm0k37mde8d9vc1j24h6jiv1', '216.73.216.60', '1760433442', '1760433442', '/index.php?XTCsid=705a3b68bece48fd9b67e5e30d623e8e&cat=c13_Accessoires.html&language=de')

[XT SQL Error]