Stepper: renaming happening without reason, leading to bug

[martin-henz]

https://share.sourceacademy.org/2vmmx

function rev(xs, result) {
    draw_data(xs, result);
    return is_null(xs)
           ? result
           : rev(tail(xs), pair(head(xs), result));
}

function reverse(xs) {
    return rev(xs, null);
}

reverse(list(1, 2, 3, 4));

gives:

with both rev and reverse renamed to reverse_1.