Delete queries error

With the latest version the database schema has changed. The actual data is stored in the new table query_storage. The queries is a view only from which you can't delete queries anymore. Furthermore, the client information is not stored in query_storage as IP but rather an ID linked to the new client_by_id table.
You need to do two things now:

sqlite3 /etc/pihole/pihole-FTL.db "DELETE FROM query_storage WHERE client='';"

To delete the remaining queries for before the update.

From now on you need to perform:

sqlite3 /etc/pihole/pihole-FTL.db "DELETE FROM query_storage where client in (select id from client_by_id where ip='');"