py,st3m: MenuController: Don't handle input when the view isn't active

Fixes a bug with launching the application second time if the user
presses the button again during the transition. The bug has existed
before, but got much easier to trigger with ViewManager improvements.

python_payload/st3m/ui/menu.py

@@ -203,6 +203,9 @@ class MenuController(BaseView):
 
         self._scroll_controller.think(ins, delta_ms)
 
+        if not self.is_active():
+            return
+
         target = self._scroll_controller.target_position()
 
         if self.input.buttons.app.middle.pressed: