fix(datepicker): 当没有传递value / defaultValue时渲染0的问题

[Ryan-CW-Code]

🤔 这个变动的性质是？

• 新特性提交
• 日常 bug 修复
• 站点、文档改进
• 演示代码改进
• 组件样式/交互改进
• TypeScript 定义更新
• 包体积优化
• 性能优化
• 功能增强
• 国际化改进
• 重构
• 代码风格优化
• 测试用例
• 分支合并
• 其他改动（是关于什么的改动？）

🔗 相关 Issue

1814

💡 需求背景和解决方案

☑️ 请求合并前的自查清单

⚠️ 请自检并全部勾选全部选项。⚠️

• 文档已补充或无须补充
• 代码演示已提供或无须提供
• TypeScript 定义已补充或无须补充
• fork仓库代码是否为最新避免文件冲突
• Files changed 没有 package.json lock 等无关文件

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f6675e0) 74.59% compared to head (5a8e74d) 74.58%.
Report is 2 commits behind head on next.

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #1819      +/-   ##
==========================================
- Coverage   74.59%   74.58%   -0.01%     
==========================================
  Files         215      215              
  Lines        8651     8650       -1     
  Branches     2476     2475       -1     
==========================================
- Hits         6453     6452       -1     
  Misses       1986     1986              
  Partials      212      212              

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