[9.20] fix: usr: Prevent assertion failures of dig when server is specified before...

Previously, :iscman:`dig` could exit with an assertion failure when the server was specified before the :option:`dig -b` option. This has been fixed.

Closes #5609

Backport of MR !11183

Merge branch 'backport-5609-fix-dig-crash-with-at-and-dash-b-on-main-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!11204