Gtk::TreeSelection problem

[Phil Wolff <adiabat centurylink net>]

    int n = m_refFileSelection->count_selected_rows ();
    if ( n == 1 ) {
        Gtk::TreeIter iter = m_refFileSelection->get_selected ();
        if ( iter )  {
            m_refFileSelection->unselect ( iter );
        }
    }

and

    int n = m_refFileSelection->count_selected_rows ();
    if ( n != 0 ) {
        m_refFileSelection->unselect_all ();
    }

Both of these code snippets generate the following two error messages: