fix(module: select): NotifyFieldChanged on null Values

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• New feature
• Bug fix
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🔗 Related issue link

💡 Background and solution

When making a custom input component that required support for both a single Value as well as multiple Values, I encountered the problem that setting SelectBase's Values to null (in the case I was using only a single Value would call NotifyFieldChanged. Since the field didn't actually change, but the component was rerendered on a validation state change, this resulted in an infinite loop.
I added a case for when both value and _selectedValues are null, in which case NotifyFieldChanged is not called.

📝 Changelog

EditContext.NotifyFieldChanged is no longer called when Values is kept null.

Language	Changelog
🇺🇸 English	Fix incorrect call of EditContext.NotifyFieldChanged when SelectBase.Values is set (unchanged) to null
🇨🇳 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

Patch coverage: 61.53% and project coverage change: -1.43 ⚠️

Comparison is base (4fcfc02) 45.96% compared to head (f48f475) 44.53%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3277      +/-   ##
==========================================
- Coverage   45.96%   44.53%   -1.43%     
==========================================
  Files         557      557              
  Lines       26734    26738       +4     
  Branches      266      266              
==========================================
- Hits        12288    11909     -379     
- Misses      14406    14789     +383     
  Partials       40       40              

Impacted Files	Coverage Δ
components/select/SelectBase.cs	75.73% <61.53%> (-0.47%)	⬇️

... and 23 files with indirect coverage changes

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