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', 'l6srdg3l6c9masei1vsmq5nhp2', '216.73.216.180', '1767408838', '1767408838', '/index.php?XTCsid=14a7d2371c686363b43a803ce20bf936')

[XT SQL Error]