fix: NPE when saving system configuration

[guqing]

What type of PR is this?

/kind bug
/area core
/milestone 2.18.x

What this PR does / why we need it:

修复保存系统配置时出现的 NPE 问题

此问题由于 PR #6346 导致

Which issue(s) this PR fixes:

Fixes #6416

Does this PR introduce a user-facing change?

None

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[ruibaby]

/lgtm

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 58.33%. Comparing base (bc10336) to head (70a0d3f).
Report is 97 commits behind head on main.

Files	Patch %	Lines
...halo/app/plugin/DefaultReactiveSettingFetcher.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6417      +/-   ##
============================================
+ Coverage     54.51%   58.33%   +3.82%     
- Complexity     3523     3766     +243     
============================================
  Files           646      646              
  Lines         21862    21986     +124     
  Branches       1528     1546      +18     
============================================
+ Hits          11917    12825     +908     
+ Misses         9328     8539     -789     
- Partials        617      622       +5     

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[JohnNiang]

/lgtm

[f2c-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JohnNiang

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