fix: use the cluster namespace if the secret-ref namespace of the TLS issuer is not set

[leon-inf]

close #9784

[apecloud-bot]

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Usage:
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[leon-inf]

/pick release-1.0

[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.77%. Comparing base (3c80e71) to head (7085c22).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...ollers/apps/component/transformer_component_tls.go	0.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9791      +/-   ##
==========================================
+ Coverage   59.60%   59.77%   +0.16%     
==========================================
  Files         551      551              
  Lines       59762    59766       +4     
==========================================
+ Hits        35624    35726     +102     
+ Misses      20884    20796      -88     
+ Partials     3254     3244      -10     

Flag	Coverage Δ
unittests	59.77% <0.00%> (+0.16%)	⬆️

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[apecloud-bot]

/cherry-pick release-1.0

[apecloud-bot]

🤖 says: cherry pick action finished successfully 🎉!
See: https://github.com/apecloud/kubeblocks/actions/runs/18394259044