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', '2qrif68q3arqm1pmulg1ng0ea3', '216.73.216.40', '1773636342', '1773636342', '/products_new.php?XTCsid=c407ede434192d8d024c7c2f06b2be8c')

[XT SQL Error]