### 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_taa;
}
void Viewport::set_use_debanding(bool p_use_debanding) {
	if (use_debanding == p_use_debanding) {
		return;
	}
	use_debanding = p_use_debanding;
	RS::get_singleton()->viewport_set_use_debanding(viewport, p_use_debanding);
}
bool Viewport::is_using_debanding() const {
	return use_debanding;
}
void Viewport::set_mesh_lod_threshold(float p_pixels) {
	mesh_lod_threshold = p_pixels;
	RS::get_singleton()->viewport_set_mesh_lod_threshold(viewport, mesh_lod_threshold);
}
float Viewport::get_mesh_lod_threshold() const {
	return mesh_lod_threshold;
}
void Viewport::set_use_occlusion_culling(bool p_use_occlusion_culling) {
	if (use_occlusion_culling == p_use_occlusion_culling) {
		return;
	}
	use_occlusion_culling = p_use_occlusion_culling;
	RS::get_singleton()->viewport_set_use_occlusion_culling(viewport, p_use_occlusion_culling);
	notify_property_list_changed();
}
bool Viewport::is_using_occlusion_culling() const {