[Fix]Fix pointrcnn in dev branch

[VVsssssk]

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Motivation

Fix pointrcnn model in dev branch. Add a mask for bbox after decode to avoid get inf in bbox.

Modification

Please briefly describe what modification is made in this PR.

BC-breaking (Optional)

Does the modification introduce changes that break the back-compatibility of the downstream repos?
If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

If this PR introduces a new feature, it is better to list some use cases here, and update the documentation.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[codecov]

Codecov Report

Base: 49.57% // Head: 49.59% // Increases project coverage by +0.02% 🎉

Coverage data is based on head (9e2ccbd) compared to base (7358646).
Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1874      +/-   ##
==========================================
+ Coverage   49.57%   49.59%   +0.02%     
==========================================
  Files         227      227              
  Lines       19707    19708       +1     
  Branches     3207     3207              
==========================================
+ Hits         9769     9775       +6     
+ Misses       9351     9346       -5     
  Partials      587      587              

Flag	Coverage Δ
unittests	49.59% <0.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmdet3d/models/dense_heads/point_rpn_head.py	26.62% <0.00%> (-0.18%)	⬇️
mmdet3d/datasets/pipelines/transforms_3d.py	88.25% <0.00%> (+0.85%)	⬆️

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