Handle the window being destroyed in do_synthesize_crossing_event
Handle the window being destroyed in do_synthesize_crossing_event

This can happen since we ref the window and do the function in an idle.

jadahl/gtk,Lyude/gtk-,ebassi/gtk,davidt/gtk,chergert/gtk,zsx/gtk,Lyude/gtk-,Distrotech/gtk2,Adamovskiy/gtk,davidgumberg/gtk,grubersjoe/adwaita,davidt/gtk,zsx/gtk,davidgumberg/gtk,Distrotech/gtk2,chergert/gtk,zsx/gtk,bratsche/gtk-,ahodesuka/gtk,ebassi/gtk,nacho/gtk-,Lyude/gtk-,Adamovskiy/gtk,Sidnioulz/SandboxGtk,Unity-Technologies/gtk,Lyude/gtk-,msteinert/gtk,jigpu/gtk,msteinert/gtk,grubersjoe/adwaita,Unity-Technologies/gtk,Distrotech/gtk2,Sidnioulz/SandboxGtk,jadahl/gtk,Adamovskiy/gtk,jessevdk/gtk,alexlarsson/gtk,bratsche/gtk-,jessevdk/gtk,Sidnioulz/SandboxGtk,ahodesuka/gtk,Distrotech/gtk,ahodesuka/gtk,ahodesuka/gtk,chergert/gtk,davidt/gtk,jigpu/gtk,Lyude/gtk-,chergert/gtk,davidgumberg/gtk,Lyude/gtk-,grubersjoe/adwaita,msteinert/gtk,chergert/gtk,nacho/gtk-,davidgumberg/gtk,jadahl/gtk,jessevdk/gtk,zsx/gtk,simokivimaki/gtk,davidgumberg/gtk,ebassi/gtk,ahodesuka/gtk,jigpu/gtk,ahodesuka/gtk,simokivimaki/gtk,ebassi/gtk,jadahl/gtk,Unity-Technologies/gtk,chipx86/gtk,msteinert/gtk,chipx86/gtk,alexlarsson/gtk,alexlarsson/gtk,alexlarsson/gtk,nacho/gtk-,johne53/MB3Gtk-2,jigpu/gtk,Lyude/gtk-,chipx86/gtk,davidgumberg/gtk,davidt/gtk,jessevdk/gtk,Distrotech/gtk,davidgumberg/gtk,jadahl/gtk,Unity-Technologies/gtk,johne53/MB3Gtk-2,bratsche/gtk-,Sidnioulz/SandboxGtk,davidt/gtk,Distrotech/gtk2,msteinert/gtk,nacho/gtk-,Lyude/gtk-,bratsche/gtk-,Unity-Technologies/gtk,chergert/gtk,chergert/gtk,jessevdk/gtk,alexlarsson/gtk,simokivimaki/gtk,alexlarsson/gtk,grubersjoe/adwaita,davidt/gtk,ebassi/gtk,msteinert/gtk,johne53/MB3Gtk-2,jigpu/gtk,zsx/gtk,chipx86/gtk,grubersjoe/adwaita,grubersjoe/adwaita,ahodesuka/gtk,Distrotech/gtk2,simokivimaki/gtk,chergert/gtk,Distrotech/gtk,jessevdk/gtk,jigpu/gtk,nacho/gtk-,jadahl/gtk,Adamovskiy/gtk,johne53/MB3Gtk-2,jessevdk/gtk,Adamovskiy/gtk,alexlarsson/gtk,bratsche/gtk-,bratsche/gtk-,Sidnioulz/SandboxGtk,jadahl/gtk,Distrotech/gtk,Adamovskiy/gtk,grubersjoe/adwaita,ebassi/gtk,jadahl/gtk,jigpu/gtk,Adamovskiy/gtk,Distrotech/gtk,johne53/MB3Gtk-2,simokivimaki/gtk,grubersjoe/adwaita,Sidnioulz/SandboxGtk,ahodesuka/gtk,simokivimaki/gtk,jigpu/gtk,chipx86/gtk,davidgumberg/gtk,alexlarsson/gtk,Distrotech/gtk2,Adamovskiy/gtk