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', 'kglq5k4ih21emq4mhs00bllch1', '216.73.216.244', '1752206975', '1752206975', '/index.php?cat=c6_Foodstuffs.html&XTCsid=0832187515ca706758d8e1ce01e34faf')

[XT SQL Error]