Illegal offset type in isset or empty in path_metatags_html_head_alter()

I got warning message.

Warning: Illegal offset type in isset or empty in path_metatags_html_head_alter() (line 47 file modules/path_metatags/path_metatags.module).

foreach ($element['#attributes'] as $group => $value) {
  if (!empty($build_meta[$value]) && $build_meta[$value] == $group) {
    unset($head_elements[$name]);
  }
}

I think the reason of it because $value can be type of array.

I propose to add is_string() for $value.
But I'm not sure will this affect on logic.