Added missing check against null
Added missing check against null

tomasthoresen/osg,scrawl/osg,openscenegraph/osg,openscenegraph/osg,scrawl/osg,marchelbling/osg,tomasthoresen/osg,jtorresfabra/osg,scrawl/osg,marchelbling/osg,marchelbling/osg,jtorresfabra/osg,tomasthoresen/osg,tomasthoresen/osg,openscenegraph/osg,openscenegraph/osg,scrawl/osg,marchelbling/osg,jtorresfabra/osg,jtorresfabra/osg