Bugfix: Assign vector to matrix row, not to the matrix itself

This used to work, because the matrix is 1x1 anyway (with corresponding
vectors), but some time ago the matrix and vector assignment
in dune-common was reworked, and now the code does not compile
anymore.

dune/gfe/rodlocalstiffness.hh

@@ -465,7 +465,7 @@ getStrain(const std::vector<RigidBodyMotion<RT,3> >& localSolution,
         // multiply with jacobian inverse
         Dune::FieldVector<double,1> tmp(0);
         inv.umv(shapeGrad[dof][0], tmp);
-        shapeGrad[dof] = tmp;
+        shapeGrad[dof][0] = tmp;
 
     }