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', 'elht3699o3ve4epkvps72e28p0', '216.73.216.147', '1751833632', '1751833632', '/popup_content.php?coID=1&XTCsid=0832187515ca706758d8e1ce01e34faf')

[XT SQL Error]