Fix signalled bridge/tunnel not always being redrawn on (un)reservation.

src/train_cmd.cpp

@@ -3231,6 +3231,7 @@ static bool CheckTrainStayInWormHolePathReserve(Train *t, TileIndex tile)
 		if (reserved == TRACKDIR_BIT_NONE) {
 			/* next tile is not reserved, so reserve the exit tile */
 			SetTunnelBridgeReservation(tile, true);
+			MarkTileDirtyByTile(tile);
 		}
 	}
 	bool ok = TryPathReserve(t);