Incompatibility with i3wm manager

## Prerequisites
- [x] I have searched open and closed issues for duplicates.

## Describe the bug
Using elementary theme with i3wm causes a big black border

### To Reproduce

Run Akira on i3wm https://github.com/akiraux/Akira/issues/395
Other software with same problem https://github.com/alainm23/planner/issues/303

### Expected behavior
Not to see a big black border

### Screenshots or screen recordings

### Logs

## Platform Information
App forcing to use elementary theme suffer this problem.

- [x] I'm using the latest version from git that I've manually compiled
- [x] I'm using the latest released stable version

## Additional context
There are some supposed workarounds, basically:

~/.config/gtk-3.0/gtk.css
```
window decoration {
box-shadow: none;
margin: 1px;
}
```