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', '5351298a95e6d46e7cec31b80fd0d19d', '216.73.216.213', '1767296896', '1767296896', '/shop/index.php?cPath=9_18')

[XT SQL Error]