When an asset in the current file is loaded from a user asset library,
weak references to it will have `asset_library_type` set to
`ASSET_LIBRARY_CUSTOM` and not `ASSET_LIBRARY_LOCAL`. Its
`relative_asset_identifier` will, however, be relative to the current
file (`Object/Cube`) instead of to the asset library's root
(`cube.blend/Object/Cube`). This combination makes loading such assets
from a weak reference fail, leading to a null dereference when using the
Capture Screenshot Preview operator.
To fix this, make such assets be loaded with `asset_library_type` set to
`ASSET_LIBRARY_LOCAL` instead.
Pull Request: https://projects.blender.org/blender/blender/pulls/145967
227052de83