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', 'g465jtdvoqte7uct65e9seh8e7', '216.73.216.9', '1758173737', '1758173737', '/index.php?XTCsid=6c2468ca28c6c182aaed37353d32ae32&cat=c6_Foodstuffs.html&language=de')

[XT SQL Error]