Automated cherry pick of #5960: Fix panic when validating ResourceInterpreterWebhookConfiguration with unspecified service port

[seanlaii]

Cherry pick of #5960 on release-1.12.
#5960: fix validate panic when
Part of #5964
For details on the cherry pick process, see the cherry pick requests page.

`karmada-webhook`: Fixed panic when validating ResourceInterpreterWebhookConfiguration with unspecified service port.

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.50%. Comparing base (7efb13b) to head (096e936).

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Additional details and impacted files

@@              Coverage Diff              @@
##           release-1.12    #5967   +/-   ##
=============================================
  Coverage         46.49%   46.50%           
=============================================
  Files               663      663           
  Lines             54736    54748   +12     
=============================================
+ Hits              25452    25461    +9     
- Misses            27657    27660    +3     
  Partials           1627     1627           

Flag	Coverage Δ
unittests	46.50% <100.00%> (+<0.01%)	⬆️

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