Passing null to parameter #1 ($string) of type string is deprecated in Drupal\Component\Utility\Html::escape()

Problem/Motivation

I get a lot of errors
Deprecated function: htmlspecialchars(): Passing null to parameter #1 ($string) of type string is deprecated in Drupal\Component\Utility\Html::escape() (line 424 core/lib/Drupal/Component /Utility/ HTML.php).

Steps to reproduce

Leave "Trigger width" empty in settings /admin/config/media/simple-popup-blocks/manage/{your_popup}