Error `composite-coarse-to-fine` if use a dataset without dark / flat

If I try to run the CompositeCOREstimator on a dataset without dark / flat like:

    cor_options = {"side": "center",}
    corfinder = CompositeCOREstimator(
        dataset_info=my_dataset,
        theta_interval=theta,
        n_subsampling_y=n_subsampling_y,
        oversampling=oversampling,
        cor_options=cor_options,
        logger=_logger,
        take_log=take_log,
    )
    corfinder.find_cor()

Then I receive the following error:

  File "/home/payno/Documents/dev/tomography/nabu/nabu/pipeline/estimators.py", line 453, in __init__
    my_flats = load_images_from_dataurl_dict(self.dataset_info.flats)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/payno/Documents/dev/tomography/nabu/nabu/io/reader.py", line 544, in load_images_from_dataurl_dict
    chunk_reader = ChunkReader(data_url_dict, **chunk_reader_kwargs)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/payno/Documents/dev/tomography/nabu/nabu/io/reader.py", line 300, in __init__
    self._get_reader_class(files)
  File "/home/payno/Documents/dev/tomography/nabu/nabu/io/reader.py", line 345, in _get_reader_class
    ext = self._infer_file_type(files)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/payno/Documents/dev/tomography/nabu/nabu/io/reader.py", line 338, in _infer_file_type
    fname = files[sorted(files.keys())[0]].file_path()
                  ~~~~~~~~~~~~~~~~~~~~^^^