a775d58b2e
**How to reproduce the bug:**
Load the attached Blend File OR
1. Create a new World in python: bpy.data.worlds.new("Test")
2. Switch to this new world in the UI (but do nothing else to it)
3. Import in a USD file with a DomeLight (see attached file in PR)
4. Close Blender
5. Observe assert `BLI_assert(ELEM(owner_id, nullptr, id));`
The issue was caused by a assigning a regular node tree
`World->nodetree` whereas an embedded one is expected.
Pull Request: https://projects.blender.org/blender/blender/pulls/142367