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', '4klus5bec1dta7brmjm3fa9ef7', '216.73.216.9', '1757929096', '1757929096', '/index.php?XTCsid=c663f955a861ad6e7b39daffac79d6d4')

[XT SQL Error]