application: don't unconditionally unref the GMenuModel in getters
application: don't unconditionally unref the GMenuModel in getters

Both the app-menu and menubar models can be NULL, so we shouldn't
blindly unref them, since g_object_unref() doesn't cope with NULL
pointers.

bratsche/gtk-,Distrotech/gtk2,grubersjoe/adwaita,jigpu/gtk,jigpu/gtk,grubersjoe/adwaita,davidt/gtk,chergert/gtk,jadahl/gtk,Sidnioulz/SandboxGtk,davidgumberg/gtk,Adamovskiy/gtk,Distrotech/gtk2,ebassi/gtk,ebassi/gtk,Adamovskiy/gtk,Sidnioulz/SandboxGtk,bratsche/gtk-,ebassi/gtk,msteinert/gtk,alexlarsson/gtk,jadahl/gtk,Adamovskiy/gtk,Lyude/gtk-,Sidnioulz/SandboxGtk,davidgumberg/gtk,msteinert/gtk,jessevdk/gtk,Lyude/gtk-,chergert/gtk,jigpu/gtk,Adamovskiy/gtk,chergert/gtk,alexlarsson/gtk,jessevdk/gtk,jigpu/gtk,alexlarsson/gtk,Adamovskiy/gtk,davidgumberg/gtk,Distrotech/gtk2,jadahl/gtk,Sidnioulz/SandboxGtk,msteinert/gtk,bratsche/gtk-,Distrotech/gtk2,jigpu/gtk,alexlarsson/gtk,grubersjoe/adwaita,grubersjoe/adwaita,davidt/gtk,Lyude/gtk-,alexlarsson/gtk,jigpu/gtk,Sidnioulz/SandboxGtk,jigpu/gtk,jadahl/gtk,jadahl/gtk,ahodesuka/gtk,grubersjoe/adwaita,jadahl/gtk,msteinert/gtk,davidt/gtk,grubersjoe/adwaita,bratsche/gtk-,davidgumberg/gtk,Sidnioulz/SandboxGtk,davidt/gtk,chergert/gtk,ahodesuka/gtk,chergert/gtk,Lyude/gtk-,chergert/gtk,alexlarsson/gtk,ahodesuka/gtk,alexlarsson/gtk,Adamovskiy/gtk,Distrotech/gtk2,Lyude/gtk-,msteinert/gtk,ahodesuka/gtk,Adamovskiy/gtk,Adamovskiy/gtk,alexlarsson/gtk,jessevdk/gtk,jadahl/gtk,grubersjoe/adwaita,ahodesuka/gtk,davidgumberg/gtk,bratsche/gtk-,chergert/gtk,jadahl/gtk,jigpu/gtk,ebassi/gtk,grubersjoe/adwaita,ebassi/gtk,bratsche/gtk-,davidgumberg/gtk,davidgumberg/gtk,ahodesuka/gtk,ahodesuka/gtk,jessevdk/gtk,davidt/gtk,Lyude/gtk-,jessevdk/gtk,ebassi/gtk,Distrotech/gtk2,ahodesuka/gtk,Lyude/gtk-,jessevdk/gtk,chergert/gtk,msteinert/gtk,Lyude/gtk-,jessevdk/gtk,davidgumberg/gtk,davidt/gtk