message: fix crashed
  multipart::createAsyncFilePartReader("/path/to/file"); When the path "/path/to/file" is not exist. it will crashed.
diff: @@ -48,7 +48,7 @@ FileInputStream::FileInputStream(const char* filename)
  }
  FileInputStream::~FileInputStream() {
  - if(m_ownsFile) {
  + if(m_ownsFile && m_file) {
  std::fclose(m_file);
  }
  }
  @@ -94,7 +94,7 @@ FileOutputStream::FileOutputStream(const char* filename, const char* mode)
  }
  FileOutputStream::~FileOutputStream() {
  - if(m_ownsFile) {
  + if(m_ownsFile && m_file) {
  std::fclose(m_file);
  }
  }
  