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', '2fff29d9cff8151a67ebe06243167e0a', '216.73.217.75', '1789292224', '1789292224', '/shop/index.php?cat=c1_.html')

[XT SQL Error]