Can not resize sidebar when it is on right side

### Describe the bug

can't resize the sidebar when it is on the right side. I have to move it to the left, then resize, and set it on right side again.

Does not happen on a firefox profile without the theme.

### Expected behavior

I should be able to resize the sidebar.

### Screenshots

_No response_

### OS

Windows 11

### OS - Others

_No response_

### Firefox Version

118.0.2

### Distribution

- [X] [Original Lepton](https://github.com/black7375/Firefox-UI-Fix)
- [ ] [Lepton's photon style](https://github.com/black7375/Firefox-UI-Fix/tree/photon-style)
- [ ] [Lepton's proton style](https://github.com/black7375/Firefox-UI-Fix/tree/proton-style)

### Theme

- [ ] Light
- [X] Dark
- [ ] Alpenglow (System: Light)
- [ ] Alpenglow (System: Dark)
- [ ] System Default
- [ ] Others: (e.g. [Photon Colors](https://addons.mozilla.org/en-US/firefox/addon/photon-colors/), [Google Chrome Dark](https://addons.mozilla.org/en-US/firefox/addon/google-chrome-dark/), [Fairytale Of Nature](https://addons.mozilla.org/en-US/firefox/addon/fairytale-of-nature/))

### Theme - More Info

_No response_

### `user.js` setup

user.js setup

```javascript

```

### Additional context

I don't have anything set on my user.js that could affect it.
Happens on a fresh profile with 0 customization, and only the configuration from the theme.

Reproduce the issue in Firefox 118.0.2 on Windows 11 with the Original Lepton dark theme and the sidebar positioned on the right. Inspect the sidebar positioning and resizing styles, then verify that the right-side sidebar can be resized without moving it to the left.

Written by the indexing model from the issue text.