Fix UnboundLocalError when using the predict method with return_predictions=False.

[farhadrgh]

What does this PR do?

UnboundLocalError raises when using the predict method with return_predictions=False.

This is due to any_on_epoch not being defined if data_fetcher is an instance of _DataLoaderIterDataFetcher.

Fixes #20472

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📚 Documentation preview 📚: https://pytorch-lightning--20484.org.readthedocs.build/en/20484/

[lantiga]

Thanks @farhadrgh !

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79%. Comparing base (601c060) to head (9546a22).
Report is 1 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (601c060) and HEAD (9546a22). Click for more details.

HEAD has 182 uploads less than BASE

Flag	BASE (601c060)	HEAD (9546a22)
cpu	68	24
lightning	51	18
pytest	46	0
python3.9	18	6
lightning_fabric	13	0
python3.10	9	3
python3.11	18	6
python3.12	23	9
gpu	2	0

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #20484     +/-   ##
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- Coverage      88%      79%     -9%     
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  Files         267      264      -3     
  Lines       23304    23248     -56     
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- Hits        20407    18291   -2116     
- Misses       2897     4957   +2060