Error when there is only one batch

[justjhong]

silhouette_batch errors when there is only one batch:
ValueError: No objects to concatenate

We should check this edge case for the other metrics as well.

[adamgayoso]

this should also be a part of #62

[Layne-Huang]

How can we ignore the batch metrics when we only have one batch here?

[wen-zy]

How can we ignore the batch metrics when we only have one batch here?

@Layne-Huang I'm wondering if you've found a way to ignore batch metrics when there's only one batch? 🧐If you have successfully solved this problem, could you please tell me how you did it? Thank you very much! 😃