ui/app: don't implicitly redraw for each CommandEvent

Redrawing should only be scheduled when some UI state has changed.

Window has no way to know whether a CommandEvent was ignored by
the client, so push the onus to the client to schedule a redraw.

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

ui/app/window.go

@@ -242,7 +242,6 @@ func (w *Window) event(e Event) {
 		w.setNextFrame(time.Time{})
 	case *CommandEvent:
 		needAck = true
-		w.setNextFrame(time.Time{})
 	case StageEvent:
 		w.stage = e.Stage
 		if w.stage > StageDead {