message: fix borrow warning on nightly
diff: @@ -119,7 +119,7 @@ where
  let mut indptr = row_counts.clone();
  // cum sum
  for i in 1..=self.rows() {
  - indptr[i] += indptr[i - 1];
  + indptr[i] = indptr[i] + indptr[i - 1];
  }
  let nnz_max = indptr[self.rows()].index();
  let mut indices = vec![I::zero(); nnz_max];
  