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', 'j8imj606boctkl7cs0f3b0bki3', '216.73.216.60', '1760667717', '1760667717', '/product_info.php?XTCsid=3547ee950f9337e348e5e07def1466f0&info=p15_25-balloons.html&language=de')

[XT SQL Error]