fix issue for no friction case

dune/tectonic/data-structures/friction/localfriction.hh

@@ -62,7 +62,7 @@ class WrappedScalarFriction : public LocalFriction<dimension> {
   double regularity(VectorType const &x) const override {
     auto tangential_x = removeNormal(x);
     double const xnorm = tangential_x.two_norm();
-    if (xnorm <= 0.0)
+    if (xnorm < 0.0)
       return std::numeric_limits<double>::infinity();
 
     return func_.regularity(xnorm);