Linkit filter haystack error due to php 8.1

Here is a patch that fixes the issue.

Withdrawing this issue, code is working as designed. In case anyone else sees this error in php8.1 you may want to look at your twig and add a check to see if the field value is empty before rendering a "Text (formatted, long)" field in this manner:

  {% if not node.field_my_textarea.value is empty %}
      {% set my_processed_text = {
        '#type':   'processed_text',
        '#text':    node.field_my_textarea.value,
        '#format': 'rich_text',
      } %}
      {{ my_processed_text }}
  {% endif %}