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', '9l2pb3rjob2pr11djp48o3bf36', '216.73.216.9', '1757973760', '1757973760', '/shop_content.php?XTCsid=f6e58886be8011b1d9a8e232c116cb7a&coID=1')

[XT SQL Error]