Warning when saving third party settings while no settings available

Here is the test

Funny thing is that it has a mechanism with missing $configuration params

  public function prepareConfiguration($field_type, array $configuration) {
    // Fill in defaults for missing properties.
    $configuration += array(
      'label' => 'above',
      'settings' => array(),
      'third_party_settings' => array(),
    );

But the $configuration array passed already has 'settings' set to FALSE/NULL. We can fix it in prepare configuration but I think we need to deal with it at the source. But I can't find my way in the class chain.

Ok test result makes more sense, fixing it