Setting theme with +kitten themes produces empty current-theme.conf #6191

Setting color theme/scheme using kitty +kitten themes does not work since 0.28.0, it only produces an empty current-theme.conf.

To Reproduce

1. kitty +kitten themes
2. select theme
3. press m
4. an empty ~/.config/kitty/current-theme.conf has been created
5. ~/.config/kitty/kitty.conf now contains this:

# BEGIN_KITTY_THEME
# Ayu Light
include current-theme.conf
# END_KITTY_THEME

The same happened with a different theme and when directly specifying a theme: kitty +kitten themes duckbones

Environment details
I tried it on Linux (Gentoo, sway) and macOS, each with my custom config and a completely empty ~/.config/kitty/kitty.conf.