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', 'dcd6ab595c4982c30c09c52c90b452cc', '216.73.216.219', '1772242326', '1772242326', '/shop/product_info.php?info=p99_.html')

[XT SQL Error]