fix batchsampler does not work correctly

[dadwadw233]

What does this PR do?

Fixes #20326

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  • some error occured while testing (on single gpu), but it doesn't seem to have anything to do with my changes 😢

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📚 Documentation preview 📚: https://pytorch-lightning--20327.org.readthedocs.build/en/20327/

[tchaton]

Could you add a test ?

[dadwadw233]

Could you add a test ?

I added a simple test (in the latest commit) in 'test_data' which will not be passed in current version but fixed by this pr 😃

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81%. Comparing base (8ad3e29) to head (ab29ee6).

❗ There is a different number of reports uploaded between BASE (8ad3e29) and HEAD (ab29ee6). Click for more details.

HEAD has 553 uploads less than BASE

Flag	BASE (8ad3e29)	HEAD (ab29ee6)
cpu	147	21
lightning	107	16
pytest	87	2
python3.9	41	6
python3.10	42	6
lightning_fabric	25	0
python3.11	44	6
gpu	4	2
python3.12	20	3
pytorch2.1	35	12
pytest-full	64	21
pytorch_lightning	19	7
pytorch2.2	10	3
pytorch2.3	10	3
pytorch2.4	9	3

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #20327     +/-   ##
=========================================
- Coverage      89%      81%     -8%     
=========================================
  Files         267      264      -3     
  Lines       23065    23011     -54     
=========================================
- Hits        20574    18609   -1965     
- Misses       2491     4402   +1911     

[lantiga]

LGTM, thanks for the contribution!