`StatisticsComputationError` for splits with 1 sample
For splits with 1 row we might get 
`StatisticsComputationError: Unexpected result for column_name='audio': Some measures among minimum=694.0, maximum=694.0, mean=694.0, median=694.0, std=None are None but not all of them.`
Because std for 1 sample is None and I made a check to allow this only if all samples in a split are equal to None.
example: https://huggingface.co/datasets/Aryelissa/LilFuub

A bit related to https://github.com/huggingface/datasets-server/issues/2631
`StatisticsComputationError` for splits with 1 sample: For splits with 1 row we might get 
`StatisticsComputationError: Unexpected result for column_name='audio': Some measures among minimum=694.0, maximum=694.0, mean=694.0, median=694.0, std=None are None but not all of them.`
Because std for 1 sample is None and I made a check to allow this only if all samples in a split are equal to None.
example: https://huggingface.co/datasets/Aryelissa/LilFuub

A bit related to https://github.com/huggingface/datasets-server/issues/2631