Fix yielding from iterator in LiteDataLoader

[awaelchli]

What does this PR do?

Fixes an issue with yielding in the iterator if device=None (no automatic device placement).
The test on master raises StopIteration on the first batch.

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Did you have fun?

I made sure I had fun coding 🙃

Part of #1 (it's a lie, this is just here to avoid noisy GitHub bot)

[tchaton]

LGMT !