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', '1u6lafakrct76p2amo05e0dir6', '216.73.216.63', '1774090335', '1774090335', '/shop_content.php?XTCsid=85f438a686cbfb5e3ea5e5d6b9611958&coID=2')

[XT SQL Error]