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', 'nn5rfcg39l2g2qhpn9qmcqvvt2', '216.73.216.180', '1766527961', '1766527961', '/index.php?XTCsid=593fd2e17068b694f72d0281fb0f8bdf')

[XT SQL Error]