Fix: handle 0 session case in ask new streams

If all sessions are closed by the time we ask for new streams, we could
end up looping forever waiting for new streams, so we now check we are
still waiting for something before looping.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>