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', '3h0jegvf31mqignicdnjeoepi1', '216.73.216.160', '1752545815', '1752545815', '/index.php?XTCsid=a924573fe10757aaf06546849adfbfb8')

[XT SQL Error]