### 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 offset;
}
void Camera2D::set_anchor_mode(AnchorMode p_anchor_mode) {
	anchor_mode = p_anchor_mode;
	_update_scroll();
}
Camera2D::AnchorMode Camera2D::get_anchor_mode() const {
	return anchor_mode;
}
void Camera2D::set_ignore_rotation(bool p_ignore) {
	ignore_rotation = p_ignore;
	Point2 old_smoothed_camera_pos = smoothed_camera_pos;
	
	if (ignore_rotation) {
		camera_angle = 0.0;
	}
	_update_scroll();
	smoothed_camera_pos = old_smoothed_camera_pos;
}
bool Camera2D::is_ignoring_rotation() const {
	return ignore_rotation;
}
void Camera2D::set_process_callback(Camera2DProcessCallback p_mode) {
	if (process_callback == p_mode) {
		return;
	}
	process_callback = p_mode;
	_update_process_callback();
}
void Camera2D::set_enabled(bool p_enabled) {