Avoid changing the result in ignored nodes.

dune/matrix-vector/triangularsolve.hh

@@ -12,7 +12,6 @@ namespace MatrixVector {
   static void lowerTriangularSolve(Matrix const& L, Vector b, Vector& x,
                                    BitVector const* ignore,
                                    bool transpose = false) {
-    x = 0;
     if (transpose) {
       for (auto it = L.begin(); it != L.end(); ++it) {
         const size_t i = it.index();
@@ -55,7 +54,6 @@ namespace MatrixVector {
   static void upperTriangularSolve(Matrix const& U, Vector b, Vector& x,
                                    BitVector const* ignore,
                                    bool transpose = false) {
-    x = 0;
     if (transpose) {
       for (auto it = U.beforeEnd(); it != U.beforeBegin(); --it) {
         const size_t i = it.index();