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', '8e649892923095fefcf66abaeab67a8a', '216.73.216.169', '1755543462', '1755543462', '/shop/product_info.php?info=p42_.html')

[XT SQL Error]