### 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)
canvas_layer_transform = E->get_final_transform();
					canvas_layer_id = E->get_instance_id();
				} else {
					
					canvas_layer_transform = get_canvas_transform();
					canvas_layer_id = ObjectID();
				}
				Vector2 point = canvas_layer_transform.affine_inverse().xform(pos);
				PhysicsDirectSpaceState2D::PointParameters point_params;
				point_params.position = point;
				point_params.canvas_instance_id = canvas_layer_id;
				point_params.collide_with_areas = true;
				point_params.pick_point = true;
				int rc = ss2d->intersect_point(point_params, res, 64);
				for (int i = 0; i < rc; i++) {
					if (res[i].collider_id.is_valid() && res[i].collider) {
						CollisionObject2D *co = Object::cast_to<CollisionObject2D>(res[i].collider);
						if (co && co->can_process()) {
							bool send_event = true;
							if (is_mouse) {
								HashMap<ObjectID, uint64_t>::Iterator F = physics_2d_mouseover.find(res[i].collider_id);
								if (!F) {
									physics_2d_mouseover.insert(res[i].collider_id, frame);
									co->_mouse_enter();
								} else {
									F->value = frame;
									
									if (mm.is_valid() && mm->get_device() == InputEvent::DEVICE_ID_INTERNAL) {
										send_event = false;