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', '1e9hchtsmoavj10flukac01hg5', '216.73.216.127', '1752881704', '1752881704', '/index.php?XTCsid=1e57725f188b4dbbf7e4ab8cd5d673d1')

[XT SQL Error]