[Bug] missing text when export to markdown or pdf

### Bug Description

There are some texts are missing when i export to markdown or pdf

### How to Reproduce

cd appflowy-editor/example
flutter run -d linux

import from document json
export to markdown|pdf

files:
[tttt.json](https://github.com/user-attachments/files/21594331/tttt.json)

[tttt.md](https://github.com/user-attachments/files/21594233/tttt.md)

### Expected Behavior

should be the same

### Operating System

ubuntu24

### AppFlowy Editor Version(s)

latetest

### Screenshots

### Additional Context

_No response_