### 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)
limit[SIDE_LEFT] = -10000000;
	limit[SIDE_TOP] = -10000000;
	limit[SIDE_RIGHT] = 10000000;
	limit[SIDE_BOTTOM] = 10000000;
	drag_margin[SIDE_LEFT] = 0.2;
	drag_margin[SIDE_TOP] = 0.2;
	drag_margin[SIDE_RIGHT] = 0.2;
	drag_margin[SIDE_BOTTOM] = 0.2;
	set_notify_transform(true);
	set_hide_clip_children(true);
}