f271d85b86
We cannot nuke treestore in readfile's `blo_lib_link_screen_restore()`, because this will destroy all UI-state data (like opened/closed items, etc.). Since we cannot know for sure whether an ID pointer from tselem->id is valid here, we have to ensure they are never invalid, i.e. to always set them to NULL when we delete them. To do so, this commit uses a similar approach as what already exists for ID references in WM notifiers - it extends `free_notifier_reference_cb()` to also nullify those IDs in all outliners. Note that some ID types are not used(shown) by outliner currently, so `TREESTORE_ID_TYPE` macro was added, that checks whether an ID is possibly used by outliner. Avoids a few searches in whole tree whene deleting some IDs. Reviewers: campbellbarton, sergey Maniphest Tasks: T44439 Differential Revision: https://developer.blender.org/D1272