### 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)

Ref<Font> font = get_theme_font(SNAME("font"), SNAME("Label"));
	int font_size = get_theme_font_size(SNAME("font_size"), SNAME("Label"));
	return Vector2(0, font->get_height(font_size) * 3);
}
void EditorPropertyLayersGrid::set_read_only(bool p_read_only) {
	read_only = p_read_only;
}
Size2 EditorPropertyLayersGrid::get_minimum_size() const {
	Size2 min_size = get_grid_size();
	
	if (expanded) {
		const int bsize = (min_size.height * 80 / 100) / 2;
		for (int i = 0; i < expansion_rows; ++i) {
			min_size.y += 2 * (bsize + 1) + 3;
		}
	}
	return min_size;
}
String EditorPropertyLayersGrid::get_tooltip(const Point2 &p_pos) const {