Crash when used with myrho/elm-round

[hpate-triller]

I noticed this when loading it in an app at work with myrho/elm-round. I created a small repo to reproduce it: https://github.com/hpate-triller/elm-optimize-level-2-round-bug

module Main exposing (main)

import Html
import Round


main =
    Html.text (Round.round 2 56.25)

It will crash at runtime with in this block, where it tries to call _v0.a.a.valueOf(), when this happens the str that is passed in is an empty string.

    var $myrho$elm_round$Round$round_a0 = F2(function (signed, str) {
        var _v0 = $elm$core$String$uncons(str);
        if (_v0.$ === "Nothing") {
            return false;
        }
        else {
            if ("5" === _v0.a.a.valueOf()) {
                if (_v0.a.b === "") {
                    var _v1 = _v0.a;
                    return !signed;
                }
                else {
                    var _v2 = _v0.a;
                    return true;
                }
            }
            else {
                var _v3 = _v0.a;
                var _int = _v3.a;
                return function (i) {
                    return ((i > 53) && signed) || ((i >= 53) && (!signed));
                }($elm$core$Char$toCode(_int));
            }
        }
    }), $myrho$elm_round$Round$round = $myrho$elm_round$Round$roundFun($myrho$elm_round$Round$round_a0);