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', '6406d6a0440f13a40b9b15f50c849fa9', '216.73.217.165', '1780980727', '1780980727', '/shop/index.php?cat=c29_.html')

[XT SQL Error]