peer_htlcs: Prevent htlc_out from being handled multiple times in case of immediate channeld error.

lightningd/peer_htlcs.c

@@ -349,6 +349,8 @@ static void rcvd_htlc_reply(struct subd *subd, const u8 *msg, const int *fds,
 		} else
 			local_fail_htlc(hout->in, failure_code,
 					hout->key.peer->scid);
+		/* Prevent hout from being failed twice. */
+		tal_del_destructor(hout, hout_subd_died);
 		tal_free(hout);
 		return;
 	}