app: reset Window when DestroyEvent is received

Fixes: https://todo.sr.ht/~eliasnaur/gio/595
Signed-off-by: Elias Naur <[email protected]>

Author: eliasnaur

app/window.go

@@ -617,6 +617,7 @@ func (w *Window) processEvent(e event.Event) bool {
 	case DestroyEvent:
 		w.destroyGPU()
 		w.driver = nil
+		w.basic = nil
 		if q := w.timer.quit; q != nil {
 			q <- struct{}{}
 			<-q