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', '2d27tsi032e16c8k4dr3b15me4', '216.73.217.0', '1791156600', '1791156600', '/xtshop/login.php')

[XT SQL Error]