Method operator()

apps/osvr_print_tree.cpp:74–75

@brief print nothing for a null element.

    /// @brief print nothing for a null element.
    void operator()(osvr::common::PathNode const &,
                    osvr::common::elements::NullElement const &) {}

    /// @brief We might print something for a sensor element.
    void operator()(osvr::common::PathNode const &node,