### 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)
Transform3D object_transform = p_object->get_global_transform();
	Transform3D camera_transform = p_camera->get_global_transform();
	ObjectID id = p_object->get_instance_id();
	
	if (object_transform == physics_last_object_transform && camera_transform == physics_last_camera_transform && physics_last_id == id) {
		Ref<InputEventMouseMotion> mm = p_input_event;
		if (mm.is_valid() && mm->get_device() == InputEvent::DEVICE_ID_INTERNAL) {
			return; 
		}
	}
	p_object->_input_event_call(camera_3d, p_input_event, p_pos, p_normal, p_shape);
	physics_last_object_transform = object_transform;
	physics_last_camera_transform = camera_transform;
	physics_last_id = id;
}
Camera3D *Viewport::get_camera_3d() const {