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', 'ff155tjjrcd5v6op1vnd09sct3', '216.73.216.7', '1758230498', '1758230498', '/index.php?XTCsid=0b86e5b33fa3387ebc47b5f03d369409')

[XT SQL Error]