fix(module: form): null reference exception

[ElderJames]

🤔 This is a ...

• New feature
• Bug fix
• Site / documentation update
• Demo update
• Component style update
• Bundle size optimization
• Performance optimization
• Refactoring
• Code style optimization
• Test Case
• Branch merge
• Other (about what?)

🔗 Related issue link

fiexed #3808

💡 Background and solution

📝 Changelog

Language	Changelog
🇺🇸 English
🇨🇳 Chinese

☑️ Self Check before Merge

⚠️ Please check all items below before review. ⚠️

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• Changelog is provided or not needed

[github-actions]

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 43.51%. Comparing base (88f6b90) to head (af3221a).

Files	Patch %	Lines
components/form/FormItem.razor	0.00%	0 Missing and 1 partial ⚠️
components/form/FormItem.razor.cs	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #3815       +/-   ##
===========================================
+ Coverage    1.49%   43.51%   +42.02%     
===========================================
  Files         577      580        +3     
  Lines       27928    28220      +292     
  Branches     5667     5736       +69     
===========================================
+ Hits          417    12281    +11864     
+ Misses      27471    14923    -12548     
- Partials       40     1016      +976     

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[michaelcsikos]

Can we have a NuGet release for AntDesign and AntDesign.ProLayout with this fix?

[ElderJames]

Please try the 0.19.0-rc.x release first, we will release generally available one in this week.