fix: failure to create notification templates in themes

[guqing]

What type of PR is this?

/kind bug
/area core
/milestone 2.20.x

What this PR does / why we need it:

修复主题中声明的通知模板无法被创建的问题

Which issue(s) this PR fixes:

Fixes #7195

Does this PR introduce a user-facing change?

修复主题中声明的通知模板无法被创建的问题

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

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

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

Attention: Patch coverage is 76.19048% with 10 lines in your changes missing coverage. Please review.

Project coverage is 57.23%. Comparing base (eff73dc) to head (490c25d).
Report is 86 commits behind head on main.

Files with missing lines	Patch %	Lines
...a/run/halo/app/theme/service/ThemeServiceImpl.java	76.19%	7 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7199      +/-   ##
============================================
+ Coverage     56.99%   57.23%   +0.23%     
- Complexity     3999     4049      +50     
============================================
  Files           714      719       +5     
  Lines         24110    24383     +273     
  Branches       1585     1598      +13     
============================================
+ Hits          13742    13955     +213     
- Misses         9756     9810      +54     
- Partials        612      618       +6     

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[ruibaby]

/lgtm

[f2c-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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