Only write elemsets if we actually have some to write.
Only write elemsets if we actually have some to write.

dschwen/libmesh,libMesh/libmesh,jwpeterson/libmesh,libMesh/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,dschwen/libmesh,libMesh/libmesh,dschwen/libmesh,jwpeterson/libmesh,libMesh/libmesh,jwpeterson/libmesh,dschwen/libmesh,dschwen/libmesh,dschwen/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,libMesh/libmesh,libMesh/libmesh,jwpeterson/libmesh,dschwen/libmesh,dschwen/libmesh,libMesh/libmesh,libMesh/libmesh