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', '6d5ph7joata7kb5dhjlah197i4', '216.73.216.9', '1758200587', '1758200587', '/index.php?XTCsid=57fdea81df9a3fe5bfa030cad2c80d0c')

[XT SQL Error]