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', 't8f6grdro617daejdkbau0lr10', '216.73.216.244', '1752210646', '1752210646', '/index.php?XTCsid=8a30dd886e6da2e1e68c8937ee639be6')

[XT SQL Error]