### Godot version

4.0-rc6

### System information

Fedora 37, Mesa Intel ADL GT2

### Issue description

Code that works as expected at runtime fails with Nil references to (assigned) exported vars in the editor:

![tool_global_position_error](https://user-images.githubusercontent.com/364501/222031460-ffb1ecbd-5175-4a42-8470-25285ba5f821.png)


### Steps to reproduce

Try to access the `global_position` of a `Node3D` that's assigned to an exported var.

See that it works at runtime.

See that it errors in the editor with:

> Invalid get index 'global_position' (on base: 'Nil').

### Minimal reproduction project

[tool_test.zip](https://github.com/godotengine/godot/files/10856640/tool_test.zip)

GEN_EDIT_STATE_DISABLED,
		GEN_EDIT_STATE_INSTANCE,
		GEN_EDIT_STATE_MAIN,
		GEN_EDIT_STATE_MAIN_INHERITED,
	};
	Error pack(Node *p_scene);
	void clear();
	bool can_instantiate() const;
	Node *instantiate(GenEditState p_edit_state = GEN_EDIT_STATE_DISABLED) const;
	void recreate_state();
	void replace_state(Ref<SceneState> p_by);
	virtual void reload_from_file() override;
	virtual void set_path(const String &p_path, bool p_take_over = false) override;
#ifdef TOOLS_ENABLED
	virtual void set_last_modified_time(uint64_t p_time) override {
		state->set_last_modified_time(p_time);
	}
#endif
	Ref<SceneState> get_state() const;
	PackedScene();
};
VARIANT_ENUM_CAST(PackedScene::GenEditState)
#endif