References to external actors are not removed when a data layer is deleted

Data layers still contain references to external actors when they are deleted.

1. Create a third person blueprint template project
2. Enable the "Enable Streaming" setting under world settings > world partition
3. In the content browser, Select Add > Miscellaneous > Data Layer
4. Select Window > World Partition > Data Layers Outliner
5. Right click inside the Data Layers window > Create New Data Layer, using the data layer asset
6. Select an actor in the level
7. In the Data Layers window, right click on the data layer window > Add selected actors to selected data layers
8. Delete the data layer from the Data Layers window
9. Save the level and all assets
10. Delete the data layer from the Content Browser

RESULT:
The Data Layer asset still has references to the external actor.