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', 'upc0ekrr3uaa43qsdjl7scc9q5', '216.73.216.40', '1773514462', '1773514462', '/index.php?XTCsid=25107e022e57904016ff1d84720d2d85')

[XT SQL Error]