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', '3cfqtebsju5071g4ktas0h21r5', '216.73.216.7', '1758263196', '1758263196', '/index.php?XTCsid=80c3e9fc87b53cb0d288d19ef4e9b63c&cat=c9_Tischdekoration.html&language=en')

[XT SQL Error]