### 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)
ERR_FAIL_NULL(p_control);
	ERR_FAIL_COND(!Object::cast_to<Control>((Object *)p_control));
	ERR_FAIL_COND(p_control->is_inside_tree());
	ERR_FAIL_COND(p_control->get_parent() != nullptr);
	Control *drag_preview = _gui_get_drag_preview();
	if (drag_preview) {
		memdelete(drag_preview);
	}
	p_control->set_as_top_level(true);
	p_control->set_position(gui.last_mouse_pos);
	p_base->get_root_parent_control()->add_child(p_control); 
	p_control->move_to_front();
	gui.drag_preview_id = p_control->get_instance_id();
}
Control *Viewport::_gui_get_drag_preview() {
	if (gui.drag_preview_id.is_null()) {
		return nullptr;
	} else {
		Control *drag_preview = Object::cast_to<Control>(ObjectDB::get_instance(gui.drag_preview_id));
		if (!drag_preview) {
			ERR_PRINT("Don't free the control set as drag preview.");
			gui.drag_preview_id = ObjectID();
		}
		return drag_preview;
	}
}
void Viewport::_gui_remove_root_control(List<Control *>::Element *RI) {