Assert our cache is still good

Author: roystgnr

src/mesh/mesh_base.C

@@ -516,6 +516,8 @@ void MeshBase::change_elemset_id(elemset_id_type old_id, elemset_id_type new_id)
 
 unsigned int MeshBase::spatial_dimension () const
 {
+  libmesh_assert(_preparation.has_cached_elem_data);
+
   return cast_int<unsigned int>(_spatial_dimension);
 }