### 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)
enabled = p_enabled;
	if (enabled && is_inside_tree() && !viewport->get_camera_2d()) {
		make_current();
	} else if (!enabled && is_current()) {
		clear_current();
	}
}
bool Camera2D::is_enabled() const {
	return enabled;
}
Camera2D::Camera2DProcessCallback Camera2D::get_process_callback() const {
	return process_callback;
}
void Camera2D::_make_current(Object *p_which) {
	if (p_which == this) {
		if (is_inside_tree()) {
			get_viewport()->_camera_2d_set(this);
			queue_redraw();
		}
	} else {
		if (is_inside_tree()) {
			if (get_viewport()->get_camera_2d() == this) {
				get_viewport()->_camera_2d_set(nullptr);
			}
			queue_redraw();
		}
	}
}
void Camera2D::_update_process_internal_for_smoothing() {