Function findFreeRoutingVehicleRef

src/OpenLoco/src/Vehicles/RoutingManager.cpp:9–18

    static auto& routings() { return getGameState().routings; }

    static std::optional<uint16_t> findFreeRoutingVehicleRef()
    {
        const auto& routingArr = routings();
        const auto res = std::find_if(std::begin(routingArr), std::end(routingArr), [](const auto& route) { return route[0] == kRoutingNull; });
        if (res == std::end(routingArr))
        {
            return std::nullopt;
        }
        return std::distance(std::begin(routingArr), res);
    }

    void resetRoutings(const RoutingHandle handle)
    {