fix: new tags showing null post count on theme

[guqing]

What type of PR is this?

/kind improvement
/area core
/milestone 2.20.x

What this PR does / why we need it:

修复新创建的标签在主题端展示关联文章数量为 null 的问题

仅对此 PR 之后新创建的标签有效，以前展示为 null 的标签需要手动更新一下

Which issue(s) this PR fixes:

Fixes #7042

Does this PR introduce a user-facing change?

修复新创建的标签在主题端展示关联文章数量为 null 的问题

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[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 SonarQube Cloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 57.24%. Comparing base (eff73dc) to head (0f86089).
Report is 51 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7049      +/-   ##
============================================
+ Coverage     56.99%   57.24%   +0.24%     
- Complexity     3999     4009      +10     
============================================
  Files           714      712       -2     
  Lines         24110    24148      +38     
  Branches       1585     1592       +7     
============================================
+ Hits          13742    13823      +81     
+ Misses         9756     9710      -46     
- Partials        612      615       +3     

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[JohnNiang]

针对旧数据的建议：看能否在这里判断如果为 null 则设置成 0 呢。或者直接更改对应的数据类型为 int。

halo/application/src/main/java/run/halo/app/theme/finders/vo/TagVo.java

Line 36 in 2c8f6f5

.postCount(tag.getStatusOrDefault().getVisiblePostCount())