Fixed crash on toggling the pad outline display mode in CvPcb.

pcbnew/basepcbframe.cpp

@@ -433,10 +433,13 @@ void PCB_BASE_FRAME::OnTogglePolarCoords( wxCommandEvent& aEvent )
 void PCB_BASE_FRAME::OnTogglePadDrawMode( wxCommandEvent& aEvent )
 {
     m_DisplayPadFill = DisplayOpt.DisplayPadFill = !m_DisplayPadFill;
+    EDA_DRAW_PANEL_GAL* gal = GetGalCanvas();
 
+    if( gal )
+    {
     // Apply new display options to the GAL canvas
         KIGFX::PCB_PAINTER* painter =
-            static_cast<KIGFX::PCB_PAINTER*> ( GetGalCanvas()->GetView()->GetPainter() );
+                static_cast<KIGFX::PCB_PAINTER*> ( gal->GetView()->GetPainter() );
         KIGFX::PCB_RENDER_SETTINGS* settings =
                 static_cast<KIGFX::PCB_RENDER_SETTINGS*> ( painter->GetSettings() );
         settings->LoadDisplayOptions( DisplayOpt );
@@ -448,6 +451,7 @@ void PCB_BASE_FRAME::OnTogglePadDrawMode( wxCommandEvent& aEvent )
             for( D_PAD* pad = module->Pads(); pad; pad = pad->Next() )
                 pad->ViewUpdate( KIGFX::VIEW_ITEM::GEOMETRY );
         }
+    }
 
     m_canvas->Refresh();
 }