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', 'ajnpk2gm3nua2tmga6j97m3s06', '216.73.216.33', '1770383290', '1770383290', '/xtshop/login.php')

[XT SQL Error]