alsactl: Fix potential NULL dereferences in daemon mode

The code releasing the each card object may access to NULL when a
bogus count is given.  Add a NULL check just to make sure.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

alsactl/daemon.c

@@ -451,8 +451,10 @@ save:
 out:
 	free(pfd);
 	remove(pidfile);
+	if (cards) {
 		for (i = 0; i < count; i++)
 			card_free(&cards[i]);
 		free(cards);
+	}
 	return 0;
 }