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', 'e9tic9u7n1km132l41qu0oa8j5', '216.73.216.9', '1758191443', '1758191443', '/shop_content.php?XTCsid=ca28ab8f46bb6e791b42fe9b92719761&coID=4')

[XT SQL Error]