嵌入其他筆記會導致雙欄模式下兩邊不同步

### Is this a hackmd.io issue?

- [x] Yes, the bug happens on https://hackmd.io

### What's the problem
嵌入其他筆記會導致雙欄模式下兩邊不同步

#### Current behaviour

> Screenshot (optional)


If possible, create a note with reproducible content and share the link with us.

[]https://hackmd.io/S_gWB5ZuQF2mVrAPGkBl_Q
[]https://hackmd.io/0isgLE2uQeeioFSPq5hzug

#### Expected behaviour

雙欄模式的編輯區和預覽區的最上面一行通常應該要能同步，謝謝～

#### Environment

I use HackMD on:

**Desktop**
- OS: macOS
- Browser: chrome
- Browser Version: 80.0.3987.149 (正式版本) (64 位元)