The following scenario triggers a "named" crash: 1. Configure a catalog zone. 2. Start "named". 3. Comment out the "catalog-zone" clause. 4. Run `rndc reconfig`. 5. Uncomment the "catalog-zone" clause. 6. Run `rndc reconfig` again. Implement the required cleanup of the in-memory catalog zone during the first `rndc reconfig`, so that the second `rndc reconfig` could find it in an expected state.