message: Fix unboxing_extract
diff: @@ -217,7 +217,7 @@ caf::optional<std::tuple<Ts...>> default_extract(caf_handle x) {
  template <class T>
  caf::optional<std::tuple<T>> unboxing_extract(caf_handle x) {
  auto tup = default_extract<typename T::outer_type>(x);
  - if (tup == caf::none)
  + if (tup == caf::none || !is<T>(get<0>(*tup)))
  return caf::none;
  return std::make_tuple(get<T>(get<0>(*tup)));
  }
  