Volume Rendering: don't crash if a Chunk object gets destroyed after Root has been shutdown
Volume Rendering: don't crash if a Chunk object gets destroyed after Root has been shutdown

OGRECave/ogre,paroj/ogre,paroj/ogre,OGRECave/ogre,RealityFactory/ogre,paroj/ogre,paroj/ogre,RealityFactory/ogre,RealityFactory/ogre,OGRECave/ogre,RealityFactory/ogre,RealityFactory/ogre,OGRECave/ogre,paroj/ogre,OGRECave/ogre