http-fetch segfault fix?

Pavel Roskin [off-list ref] writes:

It's a different backtrace this time.  abort_object_request() has this code:

if (obj_req->slot) {
     release_active_slot(obj_req->slot);
     obj_req->slot = NULL;
}

Apparently just because obj_req->slot is not NULL doesn't mean it's a
valid pointer.  I'm going to use Valgrind now.

Nick's one-liner to explicitly initialize newreq->slot to NULL
looks obviously correct to me.  Does it fix this problem for
you?