Dataset Viewer issue for codeparrot/xlcost-text-to-code
There seems to be an issue with the `C++-snippet-level` config:

```python
>>> from datasets import get_dataset_split_names
>>> get_dataset_split_names("codeparrot/xlcost-text-to-code", "C++-snippet-level")
Traceback (most recent call last):
  File "/home/slesage/hf/datasets-server/services/worker/.venv/lib/python3.9/site-packages/datasets/inspect.py", line 352, in get_dataset_config_info
    info.splits = {
TypeError: 'NoneType' object is not iterable

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/slesage/hf/datasets-server/services/worker/.venv/lib/python3.9/site-packages/datasets/inspect.py", line 404, in get_dataset_split_names
    info = get_dataset_config_info(
  File "/home/slesage/hf/datasets-server/services/worker/.venv/lib/python3.9/site-packages/datasets/inspect.py", line 359, in get_dataset_config_info
    raise SplitsNotFoundError("The split names could not be parsed from the dataset config.") from err
datasets.inspect.SplitsNotFoundError: The split names could not be parsed from the dataset config.
```

I remove the dataset-viewer tag since it's not directly related.

Pinging @huggingface/datasets  Thanks I found that this subset wasn't properly defined the the config, I fixed it. Now I can see the subsets but I get this error for the viewer
````
Status code:   400
Exception:     Status400Error
Message:       The split cache is empty.
``` Yes, the cache is being refreshed, hopefully, it will work in some minutes for all the splits. Some are already here:

https://huggingface.co/datasets/codeparrot/xlcost-text-to-code/viewer/Python-snippet-level/train

<img width="1533" alt="Capture d’écran 2022-07-18 à 12 04 06" src="https://user-images.githubusercontent.com/1676121/179553933-64d874fa-ada9-4b82-900e-082619523c20.png">
 I think all the splits are working as expected now Perfect, thank you!
### Link

https://huggingface.co/datasets/codeparrot/xlcost-text-to-code

### Description

Error
```
Server Error
Status code:   400
Exception:     TypeError
Message:       'NoneType' object is not iterable
```
Before I did a minor change in the dataset script (removing some comments), the viewer was working but not properely, it wasn't showing the dataset subsets. But the data can be loaded successfully.

Thanks!

### Owner

Yes