[core] fileUtils: Never call group() on an empty match

[cbentejac]

Description

This PR addresses an issue when attempting to display images in the 2D viewer while there are several CameraInit nodes in the scene.

Ensuring match is not None before calling group() prevents an AttributeError that causes the display in the viewer of the selected image to fail:

frameId_str = match.group("FRAMEID_STR")
                  ^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'group'

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.47%. Comparing base (760a240) to head (7ec748e).
⚠️ Report is 6 commits behind head on develop.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3084      +/-   ##
===========================================
+ Coverage    83.40%   83.47%   +0.06%     
===========================================
  Files           81       81              
  Lines        10259    10300      +41     
===========================================
+ Hits          8557     8598      +41     
  Misses        1702     1702              

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