html_field_formatter: breaks if allowed tags are given

Problem/Motivation

If you are using the html_field_formatter module and allowed tags in display settings, the site breaks with

TypeError: Drupal\klaro\Utility\KlaroHelper::processHtml(): Argument #1 ($html) must be of type string

Steps to reproduce

• Install klaro and html_field_formatter
• Set up an entity or media entity with html text
• configure display of this field via html_field_formatter module
• set allowed tags in html_field_formatter