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', '6kamokoa043phmcprrcb6oq1h7', '216.73.216.138', '1769675615', '1769675615', '/index.php?XTCsid=ee72fd127966305e536831aa3802aefb')

[XT SQL Error]