[Bug] In `0.9.100`, (solely `1em`) font previews render as `#000000`, which is problematic when `org.freedesktop.appearance: color-scheme: 1`.

#### Examples

This means that they are nigh unreadable.

#### My Environment

1. #### OS And DE

~~~ini
NAME="Fedora Linux"
VERSION_ID=42
VARIANT="KDE Plasma Desktop Edition"
~~~

1. #### Application

~~~YAML
ID: com.github.fontmatrix.Fontmatrix
Ref: app/com.github.fontmatrix.Fontmatrix/x86_64/stable
Arch: x86_64
Branch: stable
Version: 0.9.100
License: GPL-2.0+
Origin: flathub
Collection: org.flathub.Stable
Installation: system
Installed: 89.6 MB
Runtime: org.kde.Platform/x86_64/5.15-24.08
Sdk: org.kde.Sdk/x86_64/5.15-24.08

Commit: 5466d63f9e6d4ab7ad4a8a928c87f4206e95e203906b4961ffadae89b724cc35
Parent: 468dad10808a72811db7ed8cb340355047583e3c5accdd6baa38070ebfd1a8c9
Subject: Update to runtime 24.08 (c3722a73f3dd)
Date: 2025-06-29 02:09:01 +0000
~~~