[Bug fix] Fix backward Euler output

src/timestepping/backward_euler.cc

@@ -122,7 +122,7 @@ void BackwardEuler<Vector, Matrix, Function, dim>::extractRelativeDisplacement(
     DUNE_THROW(Dune::Exception,
                "It seems you forgot to call postProcessRelativeQuantities!");
 
-  displacement = u;
+  displacement = ur;
 }
 
 template <class Vector, class Matrix, class Function, size_t dim>