GtkFontButton: Avoid criticals
GtkFontButton: Avoid criticals

The font_family and font_face members may be NULL, and we
shouldn't cause critical warnings in that case.

Adamovskiy/gtk,Lyude/gtk-,jessevdk/gtk,chergert/gtk,jigpu/gtk,chergert/gtk,ahodesuka/gtk,Adamovskiy/gtk,Lyude/gtk-,Adamovskiy/gtk,Lyude/gtk-,alexlarsson/gtk,jadahl/gtk,grubersjoe/adwaita,ahodesuka/gtk,alexlarsson/gtk,Adamovskiy/gtk,Adamovskiy/gtk,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,davidgumberg/gtk,davidgumberg/gtk,grubersjoe/adwaita,alexlarsson/gtk,jigpu/gtk,davidgumberg/gtk,jadahl/gtk,davidgumberg/gtk,jadahl/gtk,davidgumberg/gtk,Lyude/gtk-,jadahl/gtk,davidgumberg/gtk,alexlarsson/gtk,ahodesuka/gtk,alexlarsson/gtk,jessevdk/gtk,alexlarsson/gtk,Adamovskiy/gtk,ahodesuka/gtk,grubersjoe/adwaita,grubersjoe/adwaita,jessevdk/gtk,Adamovskiy/gtk,chergert/gtk,grubersjoe/adwaita,Lyude/gtk-,jigpu/gtk,ahodesuka/gtk,Lyude/gtk-,jessevdk/gtk,jigpu/gtk,jigpu/gtk,alexlarsson/gtk,jadahl/gtk,Lyude/gtk-,jessevdk/gtk,alexlarsson/gtk,davidgumberg/gtk,Lyude/gtk-,chergert/gtk,Adamovskiy/gtk,chergert/gtk,chergert/gtk,chergert/gtk,jadahl/gtk,ahodesuka/gtk,jigpu/gtk,davidgumberg/gtk,jigpu/gtk,ahodesuka/gtk,ahodesuka/gtk,jadahl/gtk,chergert/gtk,jadahl/gtk,jessevdk/gtk,jigpu/gtk,jessevdk/gtk