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', '9ubgk9rnlu4a96ialvlkl5uj34', '216.73.216.28', '1765373046', '1765373046', '/index.php?XTCsid=0b86e5b33fa3387ebc47b5f03d369409')

[XT SQL Error]