Define drawing function of CellularPanel, which visits nodes

src/TrackPanel.cpp

@@ -1666,6 +1666,21 @@ void TrackPanel::OnTrackFocusChange( wxCommandEvent &event )
    }
 }
 
+TrackPanelDrawable::~TrackPanelDrawable()
+{
+}
+
+void TrackPanelDrawable::Draw(
+   TrackPanelDrawingContext &, const wxRect &, unsigned )
+{
+}
+
+wxRect TrackPanelDrawable::DrawingArea(
+   const wxRect &rect, const wxRect &, unsigned )
+{
+   return rect;
+}
+
 TrackPanelNode::TrackPanelNode()
 {
 }