message: To fix bug which is a validation for the potential null pointer.
diff: @@ -228,7 +228,7 @@ void SparseMat::create(int d, const int* _sizes, int _type)
  }
  }
  int _sizes_backup[CV_MAX_DIM]; // #5991
  - if (_sizes == hdr->size)
  + if (hdr && _sizes == hdr->size)
  {
  for(int i = 0; i < d; i++ )
  _sizes_backup[i] = _sizes[i];
  