bigl2::lattice_reduce infinite loop

[andersk]

This test loops infinitely:

use lll_rs::{l2::bigl2, matrix::Matrix, vector::BigVector};
use rug::Assign;

fn main() {
    let mut basis: Matrix<BigVector> = Matrix::init(3, 4);
    basis[0][0].assign(1);
    basis[0][3].assign(1);
    basis[1][1].assign(1);
    basis[1][3].assign(5);
    basis[2][2].assign(1);
    basis[2][3].assign(9);
    bigl2::lattice_reduce(&mut basis, 0.6, 0.95);
}

[Ashashin]

Thank you for your feedback. It was indeed a small mistake on my side. It will be fixed once the PR is approved.