chore: support empty password when system account refers the custom secret

[wangyelei]

redis supports empty password

[apecloud-bot]

Auto Cherry-pick Instructions

Usage:
  - /nopick: Not auto cherry-pick when PR merged.
  - /pick: release-x.x [release-x.x]: Auto cherry-pick to the specified branch when PR merged.

Example:
  - /nopick
  - /pick release-1.0

[wangyelei]

/approved

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 50.98%. Comparing base (d144cac) to head (2ae8dff).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...rs/apps/component/transformer_component_account.go	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9911      +/-   ##
==========================================
- Coverage   51.02%   50.98%   -0.04%     
==========================================
  Files         541      541              
  Lines       58287    58294       +7     
==========================================
- Hits        29740    29722      -18     
- Misses      25602    25656      +54     
+ Partials     2945     2916      -29     

Flag	Coverage Δ
unittests	50.98% <0.00%> (-0.04%)	⬇️

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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/19952291243