BuildData needs to be released from level when it is unloaded

User is not able to load a build data asset without loading the level first. This can cause issues when trying to manage Source Control with the asset.

1. Open Content Examples in editor.
2. Sign into Source Control.
3. Open any map.
4. Build lighting.
5. Save and checkout the map and it's Build Data Registry asset.
6. Open up another map.
7. Right-click the Build Data asset.

RESULT:

Asset couldn't be loaded.

WORKAROUND:

Right-click the associated map.