Issue with Syntax module - when trying to replace a highlighted text, the text gets deleted

[darbentov]

Hi, I'm using the Syntax module in order to do syntax highlighting of code blocks.
I stumbled upon an issue where I'm trying to replace a highlighted text with a different text, the text gets deleted.

Link to demo:
https://codesandbox.io/s/quill-with-syntax-highlighting-bug-when-trying-to-replace-an-highlighted-text-x5uw9?file=/src/syntax.js

Steps to reproduce:

1. Write console.log("hi"); inside the quill editor
2. Click on the "code" formatting
3. Select the highlighted text
4. Press any letter instead
5. The text will get deleted.

This is the result after typing "a":

[ronzip]

+1

[luin]

Fixed in #3807. Feel free to let me know if there is anything missing. Closing