Enable DofMap::dof_indices on NULL Elem
Enable DofMap::dof_indices on NULL Elem

This is now useful for getting just the indices of SCALAR dofs.

Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh,Mbewu/libmesh