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', 'mim6s1a5hu8ncpjp1ru8f4fq02', '216.73.216.9', '1758167988', '1758167988', '/index.php?XTCsid=88b83a19887b09d0be81a5bc76327077')

[XT SQL Error]