### 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 sdf_scale;
}
Transform2D Viewport::get_screen_transform() const {
	return get_final_transform();
}
void Viewport::set_canvas_cull_mask(uint32_t p_canvas_cull_mask) {
	canvas_cull_mask = p_canvas_cull_mask;
	RenderingServer::get_singleton()->viewport_set_canvas_cull_mask(viewport, canvas_cull_mask);
}
uint32_t Viewport::get_canvas_cull_mask() const {
	return canvas_cull_mask;
}
void Viewport::set_canvas_cull_mask_bit(uint32_t p_layer, bool p_enable) {
	ERR_FAIL_UNSIGNED_INDEX(p_layer, 32);
	if (p_enable) {
		set_canvas_cull_mask(canvas_cull_mask | (1 << p_layer));
	} else {
		set_canvas_cull_mask(canvas_cull_mask & (~(1 << p_layer)));
	}
}
bool Viewport::get_canvas_cull_mask_bit(uint32_t p_layer) const {
	ERR_FAIL_UNSIGNED_INDEX_V(p_layer, 32, false);
	return (canvas_cull_mask & (1 << p_layer));
}
#ifndef _3D_DISABLED
AudioListener3D *Viewport::get_audio_listener_3d() const {
	return audio_listener_3d;
}
void Viewport::set_as_audio_listener_3d(bool p_enable) {