Parameter #2 $string of function explode expects string, SimpleXMLElement|null given

I've tried looking at a lot of solutions and still can't seem to find a fix for my issue. I keep getting the following error:

Parameter #2 $string of function explode expects string, SimpleXMLElement|null given. 

I've never had this issue before and it's only started appearing after updating Statamic to the latest version. This is my code within the GenerateFavicons.php:

private function createThumbnail(
    string $import,
    string $export,
    int $width,
    int $height,
    string $background,
    ?int $border
): void {
$svg = file_get_contents($import);
    if (!$svg) {
        return;
    }
    $svgObj = simplexml_load_string($svg);

    if (!$svgObj) {
        return;
    }

    $viewBox = explode(' ', $svgObj['viewBox']);
    $viewBoxWidth = intval($viewBox[2]);
    $viewBoxHeight = intval($viewBox[3]);

The error is showing for the following line of code:

$viewBox = explode(' ', $svgObj['viewBox']);

From what I've seen, a lot of people have been saying you shouldn't explode an array. I'm not quite sure where to go from here.

Thanks in advance.