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', '4kc9u9kfnghucig5bdr5nnkmn3', '216.73.216.110', '1752049622', '1752049622', '/index.php?XTCsid=e07b29ea8ec62b3899f39e64b0b0774c')

[XT SQL Error]