### 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)
if (last_id.is_valid()) {
				if (ObjectDB::get_instance(last_id) && last_object) {
					
					_collision_object_3d_input_event(last_object, camera_3d, ev, result.position, result.normal, result.shape);
					if (last_object->get_capture_input_on_drag() && mb.is_valid() && mb->get_button_index() == MouseButton::LEFT && mb->is_pressed()) {
						physics_object_capture = last_id;
					}
				}
			}
		} else {
			if (camera_3d) {
				Vector3 from = camera_3d->project_ray_origin(pos);
				Vector3 dir = camera_3d->project_ray_normal(pos);
				real_t far = camera_3d->far;
				PhysicsDirectSpaceState3D *space = PhysicsServer3D::get_singleton()->space_get_direct_state(find_world_3d()->get_space());
				if (space) {
					PhysicsDirectSpaceState3D::RayParameters ray_params;
					ray_params.from = from;
					ray_params.to = from + dir * far;
					ray_params.collide_with_areas = true;
					ray_params.pick_ray = true;
					bool col = space->intersect_ray(ray_params, result);
					ObjectID new_collider;
					CollisionObject3D *co = col ? Object::cast_to<CollisionObject3D>(result.collider) : nullptr;
					if (co && co->can_process()) {
						new_collider = result.collider_id;
						if (!capture_object) {
							last_object = co;
							last_id = result.collider_id;
							if (co->get_capture_input_on_drag() && mb.is_valid() && mb->get_button_index() == MouseButton::LEFT && mb->is_pressed()) {