[Fix] Seg tta UT & p2v_map bug when gt is none

[sunjiahao1999]

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Motivation

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Modification

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Checklist

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[codecov]

Codecov Report

Patch coverage: 8.33% and no project coverage change.

Comparison is base (260860a) 47.12% compared to head (25aa576) 47.12%.

❗ Current head 25aa576 differs from pull request most recent head 8e6c33e. Consider uploading reports for the commit 8e6c33e to get more accurate results

Additional details and impacted files

@@           Coverage Diff            @@
##           dev-1.x    #2466   +/-   ##
========================================
  Coverage    47.12%   47.12%           
========================================
  Files          276      276           
  Lines        23009    23011    +2     
  Branches      3581     3582    +1     
========================================
+ Hits         10844    10845    +1     
- Misses       11483    11484    +1     
  Partials       682      682           

Flag	Coverage Δ
unittests	47.12% <8.33%> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
mmdet3d/models/decode_heads/cylinder3d_head.py	51.35% <ø> (ø)
mmdet3d/models/decode_heads/minkunet_head.py	50.00% <0.00%> (ø)
...t3d/models/data_preprocessors/data_preprocessor.py	31.46% <9.09%> (+0.16%)	⬆️

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