fix panic of podGroup and pod delete order issue2

[buptcozy]

Ⅰ. Describe what this PR does

Ⅱ. Does this pull request fix one issue?

Ⅲ. Describe how to verify it

Ⅳ. Special notes for reviews

V. Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests
• All checks passed in make test

[codecov]

Codecov Report

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

Project coverage is 68.78%. Comparing base (a931cf2) to head (a7b96e7).

Files	Patch %	Lines
...g/scheduler/plugins/coscheduling/core/ganggroup.go	33.33%	9 Missing and 9 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2013      +/-   ##
==========================================
- Coverage   68.81%   68.78%   -0.03%     
==========================================
  Files         422      422              
  Lines       39030    39058      +28     
==========================================
+ Hits        26859    26867       +8     
- Misses       9855     9861       +6     
- Partials     2316     2330      +14     

Flag	Coverage Δ
unittests	68.78% <43.75%> (-0.03%)	⬇️

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[hormes]

/lgtm

[buptcozy]

/approve

[koordinator-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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