fixed a bug in prove_refinesEqualSubTerm and prove_refinesRefl that would crash when trying to refine an op that is undefined and has no post-condition
fixed a bug in prove_refinesEqualSubTerm and prove_refinesRefl that would crash when trying to refine an op that is undefined and has no post-condition

git-svn-id: 9ecf60ce9baff443e30a0472d3fd222fcb8117cf@9297 7b97033b-253e-4a5c-9b07-e25f9089a9fd

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