in_array(): Argument #2 ($haystack) must be of type array, Drupal\Core\Template\AttributeArray given

@geolim4, i have fixed the issue and created Patch. please review it once

Hello @abhishek_gupta1, ok for me, but wouldn't be better to use iterator_to_array() instead ?
Just in case $variables['attributes']['class'] could be a primitive array as well ?
Thank you.