This was the error on this line
$validNames = \array_slice($group, 0, $i + 1);
/home/lf1yjgi0cj08/public_html/singledosebrew.com/libraries/src/Form/Form.php:1394
// Iterate through the nested groups to find any matching form field groups.
for ($i = 1, $n = \count($group); $i < $n; $i++) {
// Initialise some loop variables.
$validNames = \array_slice($group, 0, $i + 1);
$current = $tmp;
$tmp = [];
// Check to make sure that there are no parent groups for each element.
foreach ($current as $element) {
