fix: unable to empty value when setting precision

[denghuacc]

resolve ant-design/ant-design#29754

[vercel]

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[codecov]

Codecov Report

Merging #309 (1b1c0f1) into master (163d16f) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #309      +/-   ##
==========================================
+ Coverage   97.24%   97.25%   +0.01%     
==========================================
  Files           8        8              
  Lines         399      401       +2     
  Branches      107      106       -1     
==========================================
+ Hits          388      390       +2     
  Misses         11       11              

Impacted Files	Coverage Δ
src/utils/MiniDecimal.ts	95.20% <100.00%> (+0.07%)	⬆️

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[zombieJ]

加一个 onChange 事件测试，清空时验证值为 null。

[zombieJ]

+ rc-input-number@7.0.3