Dali returns an empty connection if client connection is stale, should throw an exception.

If a client connect to SDS, with a stale connection, i.e. a connection that was established before a Dali recycle, then Dali aborts the attempt, but returns an empty connection.

Which looks indistinguishable from an attempt to connect to a xpath that is not there from the clients point of view.

Dali should throw an exception in this case.