checker, statistic: avoid leak in label statistic (#8703)

[ti-chi-bot]

This is an automated cherry-pick of #8703

What problem does this PR solve?

Issue Number: Close #8700

What is changed and how does it work?

Check List

Tests

• Unit test

Release note

None.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JmPotato, rleungx

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• OWNERS [JmPotato,rleungx]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-10-22 04:05:16.212666143 +0000 UTC m=+323916.909456764: ☑️ agreed by JmPotato.
• 2024-10-22 06:28:39.018849185 +0000 UTC m=+332519.715639807: ☑️ agreed by rleungx.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release-8.4@2d8f681). Learn more about missing BASE report.

Additional details and impacted files

@@              Coverage Diff               @@
##             release-8.4    #8735   +/-   ##
==============================================
  Coverage               ?   70.02%           
==============================================
  Files                  ?      517           
  Lines                  ?    79958           
  Branches               ?        0           
==============================================
  Hits                   ?    55988           
  Misses                 ?    20410           
  Partials               ?     3560           

Flag	Coverage Δ
unittests	70.02% <100.00%> (?)

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