`plus` constraint over unbounded variables panic with message `attempt to subtract with overflow`

[pellico]

Pumpkin version 0.3.0

use std::{i32, result, vec};

use pumpkin_solver::conflict_resolvers::resolvers::ResolutionResolver;
use pumpkin_solver::core::results::{ProblemSolution, SatisfactionResult};
use pumpkin_solver::core::termination::Indefinite;
use pumpkin_solver::*;
fn main() {
    let mut solver = Solver::default();

    // We create 3 variables
    let x = solver.new_bounded_integer(i32::MIN, i32::MAX);
    let y = solver.new_bounded_integer(i32::MIN, i32::MAX);
    let z = solver.new_bounded_integer(i32::MIN, i32::MAX);
    let c1 = solver.new_constraint_tag();
    solver.add_constraint(plus(x, y, z, c1)).post().unwrap();

    let mut termination = Indefinite;
    let mut resolver = ResolutionResolver::default();
    let mut brancher = solver.default_brancher();
    let result = solver.satisfy(&mut brancher, &mut termination, &mut resolver);
}

This panic with message:

attempt to subtract with overflow