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', '7k4871ctc4mggt7roq3c4892d5', '216.73.216.59', '1789263833', '1789263833', '/product_info.php?XTCsid=f6e58886be8011b1d9a8e232c116cb7a&info=p2_Bavarian-Pennant-Chain.html')

[XT SQL Error]