I have a Movie model with a name and release\_date attribute, and the following ActiveAdmin code

```
ActiveAdmin.register Promotion do

  index do
    actions
    column :name
    column :release_date, sortable: :release_date
  end

end 

```

When I sort by release\_date desc, entries with no date bubble to the top. I would prefer if those entries are always at the bottom, regardless of the sort order. Is there any way to specify the compare function when sorting a column?