Error if no "element" // ".t3js-banners"

Uncaught TypeError: Cannot read property 'children' of null at Object.randombanners.shuffle (randombanners.js?1523286223:10) at randombanners.js?1523286223:30 at randombanners.js?1523286223:49

Check if Element is on page

    if ($($element).length > 0) {
        for (var i = $element.children.length; i >= 0; i--) {
            $element.appendChild($element.children[Math.random() * i | 0]);
        }
    }