*: check raftcluster nil (#7054)

[ti-chi-bot]

This is an automated cherry-pick of #7054

What problem does this PR solve?

Issue Number: Close #7053

What is changed and how does it work?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• HuSharp
• JmPotato

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After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

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[HuSharp]

/test

[ti-chi-bot]

@HuSharp: No presubmit jobs available for tikv/pd@release-5.4

In response to this:

/test

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[codecov]

Codecov Report

Attention: Patch coverage is 43.75000% with 18 lines in your changes are missing coverage. Please review.

Project coverage is 74.60%. Comparing base (21b47d2) to head (ae68a09).

Files	Patch %	Lines
server/server.go	41.66%	9 Missing and 5 partials ⚠️
server/handler.go	50.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           release-5.4    #7068      +/-   ##
===============================================
- Coverage        74.80%   74.60%   -0.21%     
===============================================
  Files              265      265              
  Lines            28019    28032      +13     
===============================================
- Hits             20961    20913      -48     
- Misses            5216     5254      +38     
- Partials          1842     1865      +23     

Flag	Coverage Δ
unittests	74.60% <43.75%> (-0.21%)	⬇️

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[HuSharp]

/merge

[ti-chi-bot]

@HuSharp: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: ae68a09

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: HuSharp, JmPotato, lhy1024, rleungx

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [HuSharp,JmPotato,lhy1024,rleungx]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-09-14 02:43:34.646807839 +0000 UTC m=+669884.387231782: ☑️ agreed by rleungx.
• 2024-09-14 02:57:49.60476818 +0000 UTC m=+670739.345192118: ☑️ agreed by lhy1024.