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', '2ttllsrpt54vv3tlf5v2ggtqo7', '54.196.107.247', '1495571187', '1495571187', '/product_info.php?info=p206_Faust---Der-Tragoedie-erster-Teil.html')

[XT SQL Error]