SDLPP: Save texture before rendering

In some cases texture might be changed after render() has been called
but before renderer presented the render, causing errors.

sdlpp/sdlpp_scene.cpp

@@ -121,6 +121,7 @@ void Scene::renderScene( bool clear_renderer ) {
         SDL_RenderCopy( renderer->getRendererPtr(), background->getTexturePtr(),
                         NULL, NULL );
     for ( const auto &x : render_objects ) {
+        x->saveCurTexture();
         x->render();
     }
 }