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', 'oif7ah8rfcc0ik01407cadnts7', '216.73.216.145', '1778046439', '1778046439', '/index.php?XTCsid=23380c0ea5ceb30ea6ad18aac0802b89')

[XT SQL Error]