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', 'rn9kfce1dcop9jgh062nnnavo1', '216.73.216.131', '1790711534', '1790711534', '/index.php?XTCsid=ac1369b23120edf0063ec4033ff02fe6')

[XT SQL Error]