Property editing of `CrossAxisAlignment` doesn't work

Modifying `CrossAxisAlignment` for text on Flutter sample app throws error:

```
Another exception was thrown: Vertical RenderFlex with CrossAxisAlignment.end has a null textDirection, so the alignment cannot be resolved.
Another exception was thrown: Vertical RenderFlex with CrossAxisAlignment.start has a null textDirection, so the alignment cannot be
resolved.
```


首先在 Flutter sample app 中复现该问题，并检查 CrossAxisAlignment 的属性编辑路径。完成标准是更改对齐方式不再抛出 null textDirection 错误，并且示例文本会以所选对齐方式渲染。

由索引模型根据 Issue 内容生成。