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', 'c18d41bb761de3f0cf512a51b8f0149d', '216.73.216.219', '1772246131', '1772246131', '/shop/product_info.php?info=p124_.html')

[XT SQL Error]