resource_controller: prevent loadServerConfig from panic (#7361)

[ti-chi-bot]

This is an automated cherry-pick of #7361

What problem does this PR solve?

Issue Number: close #7360.

What is changed and how does it work?

Prevent `loadServerConfig` from panic.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• CabinfeverB
• nolouch

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[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

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1. It must be approved by the approvers firstly.
2. AFTER it has been approved by approvers, please wait for the cherry-pick merging approval from triage owners.

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[codecov]

Codecov Report

Merging #7384 (ead03d5) into release-7.5 (d0a17ca) will increase coverage by 0.02%.
The diff coverage is 66.66%.

Additional details and impacted files

@@               Coverage Diff               @@
##           release-7.5    #7384      +/-   ##
===============================================
+ Coverage        74.61%   74.63%   +0.02%     
===============================================
  Files              442      442              
  Lines            47822    47823       +1     
===============================================
+ Hits             35682    35695      +13     
+ Misses            8985     8969      -16     
- Partials          3155     3159       +4     

Flag	Coverage Δ
unittests	74.63% <66.66%> (+0.02%)	⬆️

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[nolouch]

included in #7384