Fix: set stream id in HUP case

In the case where a stream is closed when we get its first index, we
still need a valid stream_id to assign it in the right stream (channel).
In this case, it is not useful afterwards, but the debug output has the
right value instead of -1ULL.

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>