ui/app: (wayland) ensure DestroyEvent is the last event

A ToplevelClose event could end in the same batch of events as
another event, which will result in the other event being sent
after a DestroyEvent. Window assumes no event will arrive after
DestroyEvent, so ensure that property for the Wayland backend.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ui/app/os_wayland.go

@@ -310,7 +310,6 @@ func gio_onXdgSurfaceConfigure(data unsafe.Pointer, wmSurf *C.struct_xdg_surface
 func gio_onToplevelClose(data unsafe.Pointer, topLvl *C.struct_xdg_toplevel) {
 	w := winMap[topLvl]
 	w.dead = true
-	w.w.event(DestroyEvent{})
 }
 
 //export gio_onToplevelConfigure
@@ -772,6 +771,7 @@ loop:
 			break
 		}
 		if w.dead {
+			w.w.event(DestroyEvent{})
 			break
 		}
 		// Clear poll events.