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', 'ru25786rn1gcj6f0into109tu2', '216.73.217.128', '1790064709', '1790064709', '/index.php?XTCsid=38717c4dd62e88001622b2c7b8b8372a&language=de')

[XT SQL Error]