Improved handling of clean up of osg::Program/osg::Shader on closing of a graphis context.

src/osgUtil/SceneView.cpp

@@ -736,6 +736,9 @@ void SceneView::releaseAllGLObjects()
     if (!_camera) return;
    
     _camera->releaseGLObjects(_state.get());
+    
+    // we need to reset State as it keeps handles to Program objects.
+    if (_state.valid()) _state->reset();
 }