ISMN v1.2.0: error when reading dataset

[xushanthu-2014]

When I tried v1.2.0, it seems to be an error when I was reading data Data_separate_files_header_20170101_20211231_9078_Zd6I_20220911 (this is a file I downloaded from ISMN station, containing lat from 36N to 58N and lon from 11.75W to 29.5E.):

ismn_data = ISMN_Interface(data_path)
Files Processed: 100%|██████████| 321/321 [00:00<00:00, 4521.32it/s]Processing metadata for all ismn stations into folder /Users/xushan/research/TUD/ISMN_westEurope/Data_separate_files_header_20170101_20211231_9078_Zd6I_20220911.
This may take a few minutes, but is only done once...
Hint: Use `parallel=True` to speed up metadata generation for large datasets
Metadata generation finished after 0 Seconds.
Metadata and Log stored in /Users/xushan/research/TUD/ISMN_westEurope/Data_separate_files_header_20170101_20211231_9078_Zd6I_20220911/python_metadata

Traceback (most recent call last):

  File "<ipython-input-23-84af3e3a7ed0>", line 1, in <module>
    ismn_data = ISMN_Interface(data_path)

  File "/Users/xushan/opt/anaconda3/lib/python3.7/site-packages/ismn/interface.py", line 135, in __init__
    self.activate_network(network=network, meta_path=meta_path, temp_root=temp_root)

  File "/Users/xushan/opt/anaconda3/lib/python3.7/site-packages/ismn/interface.py", line 166, in activate_network
    self.__file_collection.to_metadata_csv(meta_csv_file)

  File "/Users/xushan/opt/anaconda3/lib/python3.7/site-packages/ismn/filecollection.py", line 403, in to_metadata_csv
    dfs = pd.concat(dfs, axis=0, sort=True)

  File "/Users/xushan/opt/anaconda3/lib/python3.7/site-packages/pandas/util/_decorators.py", line 311, in wrapper
    return func(*args, **kwargs)

  File "/Users/xushan/opt/anaconda3/lib/python3.7/site-packages/pandas/core/reshape/concat.py", line 304, in concat
    sort=sort,

  File "/Users/xushan/opt/anaconda3/lib/python3.7/site-packages/pandas/core/reshape/concat.py", line 351, in __init__
    raise ValueError("No objects to concatenate")

ValueError: No objects to concatenate

Can you please help me with this? Thanks!