Datasets crashing runs due to KeyError
### Describe the bug

Hi all,

I have been running into a pretty persistent issue recently when trying to load datasets. 
```python
    train_dataset = load_dataset(
        'llama-2-7b-tokenized', 
        split = 'train'
    )
```
I receive a KeyError which crashes the runs.
```
Traceback (most recent call last):
    main()

    train_dataset = load_dataset(
                    ^^^^^^^^^^^^^
    builder_instance = load_dataset_builder(
                       ^^^^^^^^^^^^^^^^^^^^^
    dataset_module = dataset_module_factory(
                     ^^^^^^^^^^^^^^^^^^^^^^^
    raise e1 from None

    ).get_module()
      ^^^^^^^^^^^^
    else get_data_patterns(base_path, download_config=self.download_config)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    return _get_data_files_patterns(resolver)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    data_files = pattern_resolver(pattern)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^
    fs, _, _ = get_fs_token_paths(pattern, storage_options=storage_options)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    paths = [f for f in sorted(fs.glob(paths)) if not fs.isdir(f)]
                               ^^^^^^^^^^^^^^

    allpaths = self.find(root, maxdepth=depth, withdirs=True, detail=True, **kwargs)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    for _, dirs, files in self.walk(path, maxdepth, detail=True, **kwargs):

    listing = self.ls(path, detail=True, **kwargs)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    "last_modified": parse_datetime(tree_item["lastCommit"]["date"]),
                                    ~~~~~~~~~^^^^^^^^^^^^^^
KeyError: 'lastCommit'
```
Any help would be greatly appreciated.

Thank you,

Enrico

### Steps to reproduce the bug

Load the dataset from the Huggingface hub.
```python
    train_dataset = load_dataset(
        'llama-2-7b-tokenized', 
        split = 'train'
    )
```

### Expected behavior

Loads the dataset.

### Environment info

datasets-2.14.3
CUDA 11.8
Python 3.11