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', '8bec4ac757304babc4f82fb8a115e120', '216.73.216.219', '1772242063', '1772242063', '/shop/index.php?cPath=3')

[XT SQL Error]