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', 'it5nhsebc3a3h1ml5npk84urq3', '216.73.216.118', '1761456509', '1761456509', '/index.php?XTCsid=49b9ec7df284d0ab18c62bd60ec0ce98')

[XT SQL Error]