Fix list syncronization with partly empty lists

[SkafteNicki]

What does this PR do?

Fixes #2463

Before submitting

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• Did you make sure to update the docs?
• Did you write any new necessary tests?

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📚 Documentation preview 📚: https://torchmetrics--2468.org.readthedocs.build/en/2468/

[codecov]

Codecov Report

Merging #2468 (e4dd328) into master (9d04667) will increase coverage by 0%.
The diff coverage is 100%.

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #2468   +/-   ##
======================================
  Coverage      69%     69%           
======================================
  Files         307     307           
  Lines       17421   17424    +3     
======================================
+ Hits        11995   11998    +3     
  Misses       5426    5426