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', 'ec13440f62efa84f422d739a927d9738', '216.73.216.213', '1767407164', '1767407164', '/shop/index.php?cPath=1')

[XT SQL Error]