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', 'r4ljloqkga3ugqkq2i62mq37i2', '216.73.216.109', '1774919090', '1774919090', '/index.php?XTCsid=c5d7c4bef81ef898ae62d01d8f198b35')

[XT SQL Error]