### 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)
return use_xr;
}
void Viewport::set_scaling_3d_mode(Scaling3DMode p_scaling_3d_mode) {
	if (scaling_3d_mode == p_scaling_3d_mode) {
		return;
	}
	scaling_3d_mode = p_scaling_3d_mode;
	RS::get_singleton()->viewport_set_scaling_3d_mode(viewport, (RS::ViewportScaling3DMode)(int)p_scaling_3d_mode);
}
Viewport::Scaling3DMode Viewport::get_scaling_3d_mode() const {
	return scaling_3d_mode;
}
void Viewport::set_scaling_3d_scale(float p_scaling_3d_scale) {
	
	
	
	scaling_3d_scale = CLAMP(p_scaling_3d_scale, 0.1, 2.0);
	RS::get_singleton()->viewport_set_scaling_3d_scale(viewport, scaling_3d_scale);
}
float Viewport::get_scaling_3d_scale() const {