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', 'ks0l4blq2gqapgsfqt9u85fdq6', '216.73.216.9', '1758216949', '1758216949', '/index.php?XTCsid=4ee4240d4b859190dc69024e020f83f9')

[XT SQL Error]