fix: 修复 lfJson2Xml 不兼容假值问题

[FanSun521]

• 修复 lfJson2Xml 不兼容假值问题 [Bug Report]: 使用lfJson2Xml方法报错 #1850
• 修复官网 demo 错误

网上转换规则：
json -> xml

xml -> json

我们目前效果:
json -> xml 和网上一致
xml -> json的时候把自闭合标签转化为了空对象 {}，我个人评估了下也 ok，不需要变

[changeset-bot]

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Latest commit: 0211699

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