Null Pointer Exception in createThumbnail() method when fetching configuration

I assigned the task myself because I plan to fix this issue and make a Merge Request.
Please do not work on this issue.

Fixed this issue. Please review MR. Thanks!

This issue is not more relevant after https://www.drupal.org/project/media_thumbnails/issues/3469479 📌 Fix phpstan issue Fixed was fixed with Drupal 11 compatibility fixes as well.

ConfigFactoryInterface's get method always returns an ImmutableConfig instance :

interface ConfigFactoryInterface {

  /**
   * Returns an immutable configuration object for a given name.
   *
   * @param string $name
   *   The name of the configuration object to construct.
   *
   * @return \Drupal\Core\Config\ImmutableConfig
   *   A configuration object.
   */
  public function get($name);
...

Closing it, thanks !

renrhaf → closed merge request !9