message: Fix string assignment from a pointer to char holding a null value
diff: @@ -158,7 +158,11 @@ public:
  typename enabled = typename std::enable_if<std::is_same<T, char>::value, void>::type
  >
  inline String& operator = (const T* str) {
  + if (str) {
  m_ptr = std::make_shared<std::string>(str);
  + } else {
  + m_ptr.reset();
  + }
  return *this;
  }
  