There's a draft that can't be deleted as a result of a SerialWork where the series was somehow deleted. It's not clear what caused this (possibly a race condition?), but it would be good to make sure that the SerialWork destroy callbacks can handle this case without throwing an error.
In order to test this, you need to delete a SerialWork with a missing series. The only way I know to do that is as follows:
Create a work.
Add a new series to that work.
Find the ID for that series.
Go into the rails console and call Series.find(id).delete.
View the work, press the "Edit" button, and then press "Delete Work."