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', '1ms7s4qvilok9qufdge152aoj2', '216.73.217.89', '1789586305', '1789586305', '/index.php?XTCsid=3eff8c99dafaea59a51de8d844315857')

[XT SQL Error]