message: Add missing default constructor
diff: @@ -29,15 +29,19 @@ public:
  /// Stores the template parameter pack.
  using signatures = detail::type_list<Sigs...>;
  + typed_actor_pointer() : view_(nullptr) {
  + // nop
  + }
  +
  template <class Supertype>
  - typed_actor_pointer(Supertype* selfptr) : view_(selfptr) {
  + explicit typed_actor_pointer(Supertype* selfptr) : view_(selfptr) {
  using namespace caf::detail;
  static_assert(
  tl_subset_of<type_list<Sigs...>, typename Supertype::signatures>::value,
  "cannot create a pointer view to an unrelated actor type");
  }
  - typed_actor_pointer(std::nullptr_t) : view_(nullptr) {
  + explicit typed_actor_pointer(std::nullptr_t) : view_(nullptr) {
  // nop
  }
  