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', '5c40b2f798cd33db8cddd32b52ad777f', '216.73.216.213', '1767340853', '1767340853', '/shop/index.php?cat=c13_.html')

[XT SQL Error]