Always return FALSE from the notebook leave_notify handler
Always return FALSE from the notebook leave_notify handler

As discussed on IRC with Benjamin, this should not make much
difference in practice, but it is more correct

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