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', 'hj7o5k8oo8h0licdohh782hi11', '18.97.14.85', '1763328596', '1763328596', '/xtshop/index.php?cat=c28_.html')

[XT SQL Error]