When Doom devours a creep which is under the control of Lifestealer via Infest, and the creep was a neutral creep with one ability, Doom loses one of his empty skill slots.

1. Have an enemy Lifestealer Infest and then Control a neutral creep with 1 spell (e.g. Centaur Conqueror)
2. Cast Devour on that creep

Result: You get the stomp ability, and your 2nd empty slot disappears completely.

Expected: The second empty slot should not disappear. It should stay empty and be visible.

This does not happen when devouring a 1-spell neutral in other ways. It only happens when the creep is controlled by Lifestealer.