text: Title: Example fails while building doc
  Body: Building the doc fails for example `40_advanced/example_single_configurations` on the current development branch
  
  [Logs here](https://github.com/automl/auto-sklearn/runs/3190465769)
  
  ```python
  ...
  generating gallery for examples/40_advanced... [ 50%] example_debug_logging.py
  
  Warning, treated as error:
  /home/runner/work/auto-sklearn/auto-sklearn/examples/40_advanced/example_single_configuration.py failed to execute correctly: Traceback (most recent call last):
    File "/home/runner/work/auto-sklearn/auto-sklearn/examples/40_advanced/example_single_configuration.py", line 75, in <module>
      print(pipeline.named_steps)
  AttributeError: 'NoneType' object has no attribute 'named_steps'
  ...
  ```
  