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', 'fvb7pvn737ptieh09sa27gbco1', '216.73.217.172', '1790629121', '1790629121', '/index.php?XTCsid=a1e615fe261b6ebee1d6d44580f7a3af')

[XT SQL Error]