Can't change indentation size

### Is this a hackmd.io issue?

- [x] Yes, the bug happens on https://hackmd.io
- [ ] No. If it's a self-hosted CodiMD instance, please fire up the issue in the repo of CodiMD: https://github.com/hackmdio/codimd

### What's the problem

#### Current behaviour

Provide steps to reproduce:

1. Go to the bottom right part of a document
2. Click on the number 4 next to "Spaces: "
3. See that it is unchanged.

#### Expected behaviour

The number should cycle through options like 1, 2, 4, 8, etc.

#### Environment

I use HackMD on:

**Desktop**
- OS: arch linux
- Browser: firefox
- Browser Version: 141