Right now whenever a new world is created in the editor we automatically spawn a SmartObjectCollection actor for it, regardless of whether there are SmartObjects on the map. The SmartObjectCollection should be created only once smart objects are added to a level.
1. Enable SmartObjects plugin in your project
2. Create an empty map
Observed: SmartObjectCollection actor gets auto-created
Expected: no SmartObjectCollection actor gets auto-created until smart objects get added to the map.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-168977 in the post.