Make compile for blocksize > 1

dune/solvers/iterationsteps/blockgssteps.hh

@@ -99,7 +99,8 @@ static constexpr double defaultCgTol = 1e-15;
 template <class MBlock, class VBlock>
 VBlock cg(const MBlock& m, VBlock r, size_t maxIter = defaultCgMaxIter,
           double tol = defaultCgTol) {
-  VBlock x = 0;
+  VBlock x;
+  x = 0;
   VBlock p = r;
   auto q = r;
   auto rOldSquared = r * r;