bug fix: logging test may fail if some config fails

[cheng-tan]

Why are these changes needed?

Related issue number

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• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b270a2e) 39.41% compared to head (527ec5b) 39.41%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1695   +/-   ##
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  Coverage   39.41%   39.41%           
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  Files          56       56           
  Lines        5990     5990           
  Branches     1334     1334           
=======================================
  Hits         2361     2361           
  Misses       3436     3436           
  Partials      193      193           

Flag	Coverage Δ
unittests	39.41% <ø> (ø)

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