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', '9i3gavq1obtlg8cvmv4gtlcu94', '216.73.216.89', '1761135468', '1761135468', '/xtshop/account.php')

[XT SQL Error]