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', 't9mt6m15vsvncq2lpjpjsb6ks3', '216.73.216.113', '1775166831', '1775166831', '/popup_content.php?XTCsid=d163dd0fc0b54bf3066f85422c77e00a&coID=1')

[XT SQL Error]