fix for complex Join evaluations: Join(Graph(?var,{}),Grap(?Var,Join(..)))
fix for complex Join evaluations: Join(Graph(?var,{}),Grap(?Var,Join(..)))

git-svn-id: 60eb48102d1ca0c284ab3654bef916b01e1b221b@1134 4f84a9ca-5c3e-0410-8a68-0bdf370325d5

nwebs/rdflib