Error on first visit to the admin page

Problem/Motivation

A very simple thing but one worth pointing out...

After a clean install and when visiting the admin page (admin/people/users/redirect/form/settings) for the first time,

I see the following message...

otice: Trying to access array offset on value of type null in Drupal\user_redirect\Form\UserRedirectSettingsForm->buildForm() (line 149 of modules/user_redirect/src/Form/UserRedirectSettingsForm.php).
Drupal\user_redirect\Form\UserRedirectSettingsForm->buildForm(Array, Object)
call_user_func_array(Array, Array) (Line: 531)
Drupal\Core\Form\FormBuilder->retrieveForm('config_settings_form', Object) (Line: 278)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 73)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 564)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)...

A subsequetn TWO MORE saves, removes the error message.