[Themes] Font size reverts when you open an inline editor

[dangoor]

Steps to reproduce:

1. Open theme settings
2. Set font size to 14px and save the change
3. Go to a file an open an inline editor
4. See that both the outer and inner editors revert to 12px font size while the inline editor is open and go back to 14px when it's closed

Possibly related to #8418

cc @MiguelCastillo

[MiguelCastillo]

@dangoor I am thinking that it is more related to this one, actually. #8381

[dangoor]

Fixed by #8492