Show a helpful error when you create a render window and forgot to initialise Root first.
Show a helpful error when you create a render window and forgot to initialise Root first.

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