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', '8uld1ok3ij2ln708molida2kh4', '3.85.92.139', '1561472700', '1561472700', '/index.php/cat/c1_Flossen.html')

[XT SQL Error]