Fix make check
Fix make check

GtkFontChooserWidget is using a GThemedIcon in its template,
so we need to ensure that the type is registered before
loading it. This was causing the defaultvalue test to fail.

grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita