When calling `destroy` on a draft then draft_id still contains old id

[leewaa]

This caught my eye since for filtering I rely on the draft_id as it is much more performant querying the database directly.

However I noticed the draft_id attribute still contains the old id of the draft which was destroyed. A simple object.draft.destroy causes this behaviour.

It would be nicer if the draft_id was nilled like any other active record object.