Volume Rendering: removed a warning
Volume Rendering: removed a warning

--HG--
branch : v1-9

jhu-lcsr-forks/ogre,jhu-lcsr-forks/ogre,vancepym/ogre,vancepym/ogre,vancepym/ogre,vancepym/ogre,jhu-lcsr-forks/ogre,jhu-lcsr-forks/ogre,vancepym/ogre,jhu-lcsr-forks/ogre