Some specific fonts crash in the font picker

[Sunspark-007]

Describe the bug
Some specific fonts in the font picker list will display incorrectly (sans when they should be a serif) and selecting them causes the flatpak to crash.

To Reproduce
Steps to reproduce the behavior:

1. Select Libertinus Serif Demi-Bold

Expected behavior
For the font to be selected.

Version:

• Foliate version: 3.2.0
• OS/Distribution and version: SteamOS 3.6.20
• Desktop environment: KDE
• Installation method: Flatpak

Additional context
https://github.com/alerque/libertinus/releases
You only need to install LibertinusSerif-Semibold.otf to test. The Regular face doesn't crash.
I am not sure where the issue is, BUT, selecting the font in Libreoffice GTK build doesn't cause a crash.. so there is a difference in the font picker code between foliate and libreoffice when it comes to selecting a font.

[johnfactotum]

LiberOffice uses its own widget, not GTK's font chooser. The font chooser in Foliate is. So this is a GTK bug.