fix: usr: Fix a bug in the statistics channel when querying zone transfers information

When querying zone transfers information from the statistics channel there was a rare possibility that `named` could terminate unexpectedly if a zone transfer was in a state when transferring from all the available primary servers had failed earlier. This has been fixed.

Closes #5198

Merge branch '5198-dns_remote_curraddr-bug-fix' into 'main'

See merge request isc-projects/bind9!10182