Added reset of _stateset to prevent the releaseGLObjects calling release on th StateSet from the destructor

src/osg/Drawable.cpp

@@ -256,6 +256,7 @@ Drawable::Drawable(const Drawable& drawable,const CopyOp& copyop):
 
 Drawable::~Drawable()
 {
+    _stateset = 0;
     Drawable::releaseGLObjects();
 }
 

src/osg/Geometry.cpp

@@ -82,6 +82,7 @@ Geometry::Geometry(const Geometry& geometry,const CopyOp& copyop):
 
 Geometry::~Geometry()
 {
+    _stateset = 0;
     Geometry::releaseGLObjects();
 }