Added handling of null dynamic_cast.
Added handling of null dynamic_cast.

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