### 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)
position_smoothing_speed = p_speed;
	_update_process_internal_for_smoothing();
}
real_t Camera2D::get_position_smoothing_speed() const {
	return position_smoothing_speed;
}
void Camera2D::set_rotation_smoothing_speed(real_t p_speed) {
	rotation_smoothing_speed = p_speed;
	_update_process_internal_for_smoothing();
}
real_t Camera2D::get_rotation_smoothing_speed() const {
	return rotation_smoothing_speed;
}
void Camera2D::set_rotation_smoothing_enabled(bool p_enabled) {
	rotation_smoothing_enabled = p_enabled;
	notify_property_list_changed();
}
bool Camera2D::is_rotation_smoothing_enabled() const {
	return rotation_smoothing_enabled;
}
Point2 Camera2D::get_camera_screen_center() const {