message: Fix bad assert that made smmp fail on non-square input
diff: @@ -133,8 +133,8 @@ pub fn numeric<
  assert!(a_data.len() == a_indptr[a_rows].index());
  assert!(b_indices.len() == b_indptr[b_rows].index());
  assert!(b_data.len() == b_indptr[b_rows].index());
  - assert!(c_indices.len() == c_indptr[b_rows].index());
  - assert!(c_data.len() == c_indptr[b_rows].index());
  + assert!(c_indices.len() == c_indptr[a_rows].index());
  + assert!(c_data.len() == c_indptr[a_rows].index());
  for elt in tmp.iter_mut() {
  *elt = N::zero();
  