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', 'l476tujdsp1tckiv3a8chelgl3', '216.73.217.68', '1789336120', '1789336120', '/index.php?XTCsid=fe62cbdaa9e53f20db8e50dc6c105126')

[XT SQL Error]