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', 'r04u59dv2mnt481h0aote0hlg4', '216.73.216.176', '1762451051', '1762451051', '/index.php?XTCsid=ca28ab8f46bb6e791b42fe9b92719761&language=de')

[XT SQL Error]