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', 'a5ob6l4vnj9lhk6r0gik850ls2', '216.73.216.43', '1789515508', '1789515508', '/index.php?XTCsid=97ccfe04b51dc1a45e1177cb04737958')

[XT SQL Error]