GtkApplicationWindow: Avoid a crash
GtkApplicationWindow: Avoid a crash

In several places, we were not correctly dealing with the
possibility of application not being set.

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