### 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)
Vector2 pos = p_pos;
	String tooltip;
	while (p_control) {
		tooltip = p_control->get_tooltip(pos);
		
		PopupMenu *menu = Object::cast_to<PopupMenu>(this);
		if (menu) {
			tooltip = menu->get_tooltip(pos);
		}
		if (r_tooltip_owner) {
			*r_tooltip_owner = p_control;
		}
		
		if (!tooltip.is_empty()) {
			break;
		}
		
		if (p_control->data.mouse_filter == Control::MOUSE_FILTER_STOP) {
			break;
		}
		if (p_control->is_set_as_top_level()) {
			break;
		}
		
		pos = p_control->get_transform().xform(pos);
		p_control = p_control->get_parent_control();
	}
	return tooltip;
}
void Viewport::_gui_show_tooltip() {