Provide a dummy for second_deriv

dune/tectonic/nicefunction.hh

@@ -15,7 +15,9 @@ class NiceFunction : public VirtualFunction<double, double> {
   virtual double leftDifferential(double s) const = 0;
   virtual double rightDifferential(double s) const = 0;
 
-  double virtual second_deriv(double s) const = 0;
+  double virtual second_deriv(double x) const {
+    DUNE_THROW(NotImplemented, "second derivative not implemented");
+  }
 };
 
 class RuinaFunction : public NiceFunction {