[9.18] fix: dev: Fix a possible crash when adding a zone while recursing

A query for a zone that was not yet loaded may yield an unexpected result such as a CNAME or DNAME, triggering an assertion failure. This has been fixed.

Closes #5357

Backport of MR !10562

Merge branch 'backport-5357-resume-qmin-cname-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!10719