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', '5lbjm35b9buig5dv97e7h03gu0', '216.73.216.60', '1760696608', '1760696608', '/index.php?XTCsid=81fba26e1f006e30d12d9ee4d58a4030&language=en')

[XT SQL Error]