### Godot version

v4.0.beta.custom_build [0a9e6e478]

### System information

Ubuntu, Nvidia, Vulkan

### Issue description

When a Camera2D is freed - either explicitly or by being a child of a scene that is being switched away from via a method like `get_tree().change_scene_to_file()` - then this camera somehow stays active instead of Godot properly switching to no-camera-mode.

`get_viewport().get_camera_2d()` then returns all sorts of funny things from `<Freed Object>`  (it's supposed to return `null`) to arbitrary nodes of the current scene (not cameras).

This can lead to crashes.

### Steps to reproduce

checkout the MRP.

note that the "Go to scene 2" button switches places after pressing it.
that is because a camera is still active that does not exist in the current tree.

restart it a couple of times and spam the "Go to scene 2" button.
notice the garbage output.

### Minimal reproduction project

[godot_4_camera_bug.zip](https://github.com/godotengine/godot/files/10560455/godot_4_camera_bug.zip)
}
	}
	Ref<InputEventGesture> gesture_event = p_event;
	if (gesture_event.is_valid()) {
		gui.key_event_accepted = false;
		_gui_cancel_tooltip();
		Size2 pos = gesture_event->get_position();
		Control *over = gui_find_control(pos);
		if (over) {
			bool stopped = false;
			if (over->can_process()) {
				gesture_event = gesture_event->xformed_by(Transform2D()); 
				pos = over->get_global_transform_with_canvas().affine_inverse().xform(pos);
				gesture_event->set_position(pos);
				stopped = _gui_call_input(over, gesture_event);
			}
			if (stopped) {
				set_input_as_handled();
			}
			return;
		}
	}
	Ref<InputEventScreenDrag> drag_event = p_event;
	if (drag_event.is_valid()) {
		const int drag_event_index = drag_event->get_index();
		ObjectID control_id = gui.touch_focus[drag_event_index];
		Control *over = control_id.is_valid() ? Object::cast_to<Control>(ObjectDB::get_instance(control_id)) : nullptr;
		if (!over) {
			over = gui_find_control(drag_event->get_position());
		}