window.onclick = disable;

function disable() {

    var z = document.querySelector("div.bundle-builder-app--bundle--error-message");

    if (z === null) {

        var y = document.querySelectorAll("button.bundle-builder-app--button.bundle-builder-app--button--increase");
        for (i = 0; i < y.length; i++) {
            y[i].disabled = "disabled";
        };

        var x = document.querySelectorAll("div.bundle-builder-app--bundle--product-add--wrapper > button");
        for (i = 0; i < x.length; i++) {
            x[i].disabled = "disabled";
        };

    } else {
        var y = document.querySelectorAll("button.bundle-builder-app--button.bundle-builder-app--button--increase");
        for (i = 0; i < y.length; i++) {
            y[i].disabled = "";
        };

        var x = document.querySelectorAll("div.bundle-builder-app--bundle--product-add--wrapper > button");
        for (i = 0; i < x.length; i++) {
            x[i].disabled = "";
        };

    }
}