Initialise all matrix entries

src/test-gradient-method.cc

@@ -292,7 +292,7 @@ void testSampleFunction3D() {
   int const dim = 3;
   typedef Dune::SampleFunctional<dim> Functional;
 
-  Functional::SmallMatrix A;
+  Functional::SmallMatrix A(0);
   A[0][0] = 3;
   A[0][1] = 1.5;
   A[1][0] = 1.5;