### 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)
#include "scene/resources/mesh.h"
#include "scene/resources/text_line.h"
#include "scene/resources/world_2d.h"
#include "scene/scene_string_names.h"
#include "servers/audio_server.h"
#include "servers/rendering/rendering_server_globals.h"
void ViewportTexture::setup_local_to_scene() {
	Node *loc_scene = get_local_scene();
	if (!loc_scene) {
		return;
	}
	if (vp) {
		vp->viewport_textures.erase(this);
	}
	vp = nullptr;
	Node *vpn = loc_scene->get_node(path);
	ERR_FAIL_COND_MSG(!vpn, "ViewportTexture: Path to node is invalid.");
	vp = Object::cast_to<Viewport>(vpn);
	ERR_FAIL_COND_MSG(!vp, "ViewportTexture: Path to node does not point to a viewport.");
	vp->viewport_textures.insert(this);
	ERR_FAIL_NULL(RenderingServer::get_singleton());
	if (proxy_ph.is_valid()) {
		RS::get_singleton()->texture_proxy_update(proxy, vp->texture_rid);
		RS::get_singleton()->free(proxy_ph);
	} else {
		ERR_FAIL_COND(proxy.is_valid()); 
		proxy = RS::get_singleton()->texture_proxy_create(vp->texture_rid);
	}
}
void ViewportTexture::set_viewport_path_in_scene(const NodePath &p_path) {