Fix batch_sampler maybe None error

[candlewill]

Fix batch_sampler maybe None error

Fixes # (issue)

#3011

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• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• Did you write any new necessary tests?

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• Core parts of the library: @BenjaminBossan

[BenjaminBossan]

Thanks a lot for creating the PR. If you could also add a unit test to test_data_loader.py, that would be great. The test could basically be the same as the example you provided in the issue.

[muellerzr]

agreed with Benjamin, let's add a test here then ✅ , thanks!

[HuggingFaceDocBuilderDev]

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[candlewill]

The unit test code is added, please help to review and merge.

[muellerzr]

Thanks! Overall this looks good to me, please run pip install -e .[quality]; make style; make quality; to fix the quality failures, and I made a comment for why the tests are failing

[BenjaminBossan]

Thanks for adding the test @candlewill. This PR is almost good to go, only the linter needs to be satisfied. This is because these lines are indented one level too far.

[candlewill]

I am sure now everything is OK, please help review again.

[muellerzr]

Thanks for adding a test!

[BenjaminBossan]

Thanks, LGTM.