### 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 path;
}
int ViewportTexture::get_width() const {
	ERR_FAIL_COND_V_MSG(!vp, 0, "Viewport Texture must be set to use it.");
	return vp->size.width;
}
int ViewportTexture::get_height() const {
	ERR_FAIL_COND_V_MSG(!vp, 0, "Viewport Texture must be set to use it.");
	return vp->size.height;
}
Size2 ViewportTexture::get_size() const {
	ERR_FAIL_COND_V_MSG(!vp, Size2(), "Viewport Texture must be set to use it.");
	return vp->size;
}
RID ViewportTexture::get_rid() const {
	if (proxy.is_null()) {
		proxy_ph = RS::get_singleton()->texture_2d_placeholder_create();
		proxy = RS::get_singleton()->texture_proxy_create(proxy_ph);
	}
	return proxy;
}
bool ViewportTexture::has_alpha() const {