### 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 scaling_3d_scale;
}
void Viewport::set_fsr_sharpness(float p_fsr_sharpness) {
	if (fsr_sharpness == p_fsr_sharpness) {
		return;
	}
	if (p_fsr_sharpness < 0.0f) {
		p_fsr_sharpness = 0.0f;
	}
	fsr_sharpness = p_fsr_sharpness;
	RS::get_singleton()->viewport_set_fsr_sharpness(viewport, p_fsr_sharpness);
}
float Viewport::get_fsr_sharpness() const {
	return fsr_sharpness;
}
void Viewport::set_texture_mipmap_bias(float p_texture_mipmap_bias) {
	if (texture_mipmap_bias == p_texture_mipmap_bias) {
		return;
	}
	texture_mipmap_bias = p_texture_mipmap_bias;
	RS::get_singleton()->viewport_set_texture_mipmap_bias(viewport, p_texture_mipmap_bias);
}
float Viewport::get_texture_mipmap_bias() const {
	return texture_mipmap_bias;
}
#endif 
void Viewport::_bind_methods() {