[Bug] customMark 的回调上无法拿到 vgrammar 的语法图元，同 extensionMark 不一致

[kkxxkk2019]

Version

latest

Link to Minimal Reproduction

none

Steps to Reproduce

目前是这么使用的：

customMark: [
  {
    style: {
      x: (datum, ctx) => {
        return ctx.vchart.getChart().getAllSeries()[0].getMarkInName('bar').getProduct().elements; 
     }
    }
  }
]

Current Behavior

customMark ctx.vchart.getChart().getAllSeries()[0].getMarkInName('bar').getProduct().elements 始终为空

Expected Behavior

可以获取到 elements

Environment

- OS:
- Browser:
- Framework:

Any additional comments?

No response