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', 'bk3vsd74lkmqqhg7u1hf5ab0o4', '216.73.216.139', '1770536947', '1770536947', '/index.php?XTCsid=3eeb6feb9f3fdb095dcf133e6414bb24')

[XT SQL Error]