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', 'a9ul5ua1b52ep2tams78kd4ed6', '216.73.216.244', '1752215326', '1752215326', '/shop_content.php?coID=8&XTCsid=2fab07f7a09b13e4ee5c8e548c6bf380')

[XT SQL Error]