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', '6h9f12b8cgue0t1udkvm9751t6', '216.73.216.9', '1758033584', '1758033584', '/index.php?XTCsid=3547ee950f9337e348e5e07def1466f0&cat=c6_Foodstuffs.html')

[XT SQL Error]