Remember to destroy the 3d dialog

If we don't call Destroy() on close event callback i'm not
able to quit fully from wx frontend if i've previously
launched the 3d viewer.

desmume/src/wxdlg/wxdlg3dViewer.cpp

@@ -275,6 +275,7 @@ void wxdlg3dViewer::OnCloseWindow( wxCloseEvent& event )
 {
 
     event.Skip();
+    Destroy();
 }