Issue wasn't directly related to material assets or the shader editor.
Simpler steps to reproduce:
- Open Asset Browser
- Change Asset Browser to different editor type
- Open new file (Ctrl+N)
The asset browser would remain in storage as inactive editor, including
pointers to the asset system. When opening a new file, the asset system
would get freed before the asset browser, which would then access
dangling pointers as part of its own freeing process.
Part of the issue is that `SpaceType.exit()` doesn't get called in this
case, which would remove the asset system references before the asset
system is freed. Will address this in a follow up in main, but best to
not depend on the `exit()` callback too much. Easy to do here.
83edd748a2