Optimize path assignment to handle point cloud in JSON without images

[sooahleex]

Summary

• Fixed the problem Handling 'point_cloud' Field in JSON Export Without Images: Import Error in Datumaro #1626

How to test

Checklist

• I have added unit tests to cover my changes.​
• I have added integration tests to cover my changes.​
• I have added the description of my changes into CHANGELOG.​
• I have updated the documentation accordingly

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below).

# Copyright (C) 2024 Intel Corporation
#
# SPDX-License-Identifier: MIT

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.17%. Comparing base (ff5fd94) to head (1d3f0cb).
Report is 17 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1643      +/-   ##
===========================================
+ Coverage    81.06%   81.17%   +0.10%     
===========================================
  Files          278      281       +3     
  Lines        32517    32780     +263     
  Branches      6607     5283    -1324     
===========================================
+ Hits         26360    26609     +249     
- Misses        4701     4721      +20     
+ Partials      1456     1450       -6     

Flag	Coverage Δ
ubuntu-20.04_Python-3.10	81.15% <100.00%> (+0.10%)	⬆️
windows-2022_Python-3.10	81.15% <100.00%> (+0.10%)	⬆️

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