fixedShearStressFvPatchVectorField: Corrected patch nuEff access

Resolves bug-report http://openfoam.org/mantisbt/view.php?id=2020

src/TurbulenceModels/turbulenceModels/derivedFvPatchFields/fixedShearStress/fixedShearStressFvPatchVectorField.C

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2011-2015 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -109,7 +109,7 @@ void Foam::fixedShearStressFvPatchVectorField::updateCoeffs()
         )
     );
 
-    scalarField nuEff(turbModel.nuEff()()[patch().index()]);
+    scalarField nuEff(turbModel.nuEff(patch().index()));
 
     const vectorField Uc(patchInternalField());