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', 'k8jn4plf7km6lihnj2jidhm9p5', '216.73.216.244', '1752201340', '1752201340', '/index.php?XTCsid=a1e615fe261b6ebee1d6d44580f7a3af')

[XT SQL Error]