Bug: setting order_by="degree" makes the empty intersection disappear

I see that you are not updating this repo but I was curious if you had an idea of a workaround I could use for what I think is a bug. If we set `order_by = "degree"` on `scale_x_upset()`, the empty intersection (movies with no genre) disappears and we have one fewer bar. This does not make sense. If we order by degree, I would expect the first bar to be the empty intersection with degree zero. Any ideas of a workaround? Thanks!

```
ggplot(tidy_movies, aes(x = Genres)) +
geom_bar() +
scale_x_upset()

ggplot(tidy_movies, aes(x = Genres)) +
geom_bar() +
scale_x_upset(order_by = 'degree')
```