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', '2na5rk8ac2fnesgsf8k0a5b043', '216.73.216.20', '1785983159', '1785983159', '/index.php?XTCsid=4783bbb94cdde4bc762fd8a3ed6a746c')

[XT SQL Error]