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', 'j5clk48upsptmtri8dfhqksq81', '216.73.216.9', '1758036780', '1758036780', '/index.php?XTCsid=97ccfe04b51dc1a45e1177cb04737958')

[XT SQL Error]