Fix pick default config name message
The error message to tell which config name to load is not displayed. 

This is because in the code it was considering the config kwargs to be non-empty, which is a special case for custom configs created on the fly. It appears after this change: https://github.com/huggingface/datasets/pull/2659

I fixed that by making the config kwargs empty by default, even if default parameters are passed

Fix https://github.com/huggingface/datasets/issues/2703