message: Fix. Now cv::Rect() is the identity under cv::Rect::operator| operation
diff: @@ -1803,12 +1803,17 @@ Rect_<_Tp>& operator &= ( Rect_<_Tp>& a, const Rect_<_Tp>& b )
  template<typename _Tp> static inline
  Rect_<_Tp>& operator |= ( Rect_<_Tp>& a, const Rect_<_Tp>& b )
  {
  + if (!a.area()) {
  + a = b;
  + }
  + else if (b.area()) {
  _Tp x1 = std::min(a.x, b.x);
  _Tp y1 = std::min(a.y, b.y);
  a.width = std::max(a.x + a.width, b.x + b.width) - x1;
  a.height = std::max(a.y + a.height, b.y + b.height) - y1;
  a.x = x1;
  a.y = y1;
  + }
  return a;
  }
  