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', 't0990r60qprcfcs8uri0um0nm5', '216.73.216.63', '1774247495', '1774247495', '/index.php?XTCsid=903d490a11e72fb45b2507d2f3478040&cat=c2_Decoration.html')

[XT SQL Error]