[bugfix] Use the proper ignoreNodes fields for gradient norm computations

[[Imported from SVN: r9909]]

dune/gfe/riemanniantrsolver.cc

@@ -331,7 +331,7 @@ void RiemannianTrustRegionSolver<GridType,TargetSpace>::solve()
             CorrectionType gradient = rhs_global;
             for (size_t j=0; j<gradient.size(); j++)
               for (int k=0; k<gradient[j].size(); k++)
-                if ((*ignoreNodes_)[j][k])
+                if ((*mgStep->ignoreNodes_)[j][k])  // global Dirichlet nodes set
                   gradient[j][k] = 0;
 
             if (this->verbosity_ == Solver::FULL and rank==0)