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', '5ce8lvr76pdhdbi7uj5capgk67', '216.73.216.105', '1789607426', '1789607426', '/product_info.php?XTCsid=363052f8eb28c495db1ddeca225278d6&info=p17_20-Tissue-Napkins.html&language=de')

[XT SQL Error]