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', 'n66dgsocjgh6rotdko33i6jt15', '216.73.216.130', '1761203110', '1761203110', '/index.php?XTCsid=0045c82a20eb26c176bef1fc0ba16df3&cat=c4_Beer-Mugs.html')

[XT SQL Error]