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', '4ffba0841ac14ef79127e56a8752e80d', '216.73.216.190', '1776277687', '1776277687', '/shop/product_info.php?info=p117_.html')

[XT SQL Error]