wayland: Use display from GdkDragContext device
wayland: Use display from GdkDragContext device

It will be useless to check the source window on the destination side,
it's at the moment always NULL. Fetch the display from the device instead,
which will be set for every GdkDragContext.

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