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', '9lubm16ufnn31r38epe6v10qc4', '216.73.216.152', '1774699387', '1774699387', '/shop_content.php?XTCsid=a6fef95dcbdcf765a3c6baf6e1fe0e25&coID=4')

[XT SQL Error]