TT#14008 fix possible segfault

Not only check for the presence of a sink, but also check for a sink FD.
Treat a sink without an FD as if there is no sink.

Closes #1401

Change-Id: I04c0be33f8cae39399674ca0a87185a729daa843
(cherry picked from commit 179b7edec1)

daemon/media_socket.c

@@ -1258,7 +1258,7 @@ static const char *kernelize_one(struct rtpengine_target_info *reti, GQueue *out
 
 output:
 	// output section
-	if (non_forwarding) // also applies to sink == NULL
+	if (non_forwarding || !sink || !sink->selected_sfd)
 		return NULL; // no output
 	if (!PS_ISSET(sink, FILLED))
 		return NULL;