message: dnn: fix build (nullptr issue)
diff: @@ -287,7 +287,7 @@ public:
  CV_Assert(imInfo.total() >= 2);
  // We've chosen the smallest data type because we need just a shape from it.
  // We don't allocate memory but just need the shape is correct.
  - Mat fakeImageBlob(shape(1, 1, imInfo.at<float>(0), imInfo.at<float>(1)), CV_8UC1, nullptr);
  + Mat fakeImageBlob(shape(1, 1, imInfo.at<float>(0), imInfo.at<float>(1)), CV_8UC1, NULL);
  // Generate prior boxes.
  std::vector<Mat> layerInputs(2), layerOutputs(1, priorBoxes);
  