### 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)
if (camera_3d_override) {
		if (camera_3d_override.size == p_size && camera_3d_override.z_near == p_z_near &&
				camera_3d_override.z_far == p_z_far && camera_3d_override.projection == Camera3DOverrideData::PROJECTION_ORTHOGONAL) {
			return;
		}
		camera_3d_override.size = p_size;
		camera_3d_override.z_near = p_z_near;
		camera_3d_override.z_far = p_z_far;
		camera_3d_override.projection = Camera3DOverrideData::PROJECTION_ORTHOGONAL;
		RenderingServer::get_singleton()->camera_set_orthogonal(camera_3d_override.rid, camera_3d_override.size, camera_3d_override.z_near, camera_3d_override.z_far);
	}
}
void Viewport::set_disable_3d(bool p_disable) {
	disable_3d = p_disable;
	RenderingServer::get_singleton()->viewport_set_disable_3d(viewport, disable_3d);
}
bool Viewport::is_3d_disabled() const {
	return disable_3d;
}
bool Viewport::is_camera_3d_override_enabled() const {