Caused by 23835a393c, which removed entirely the transitive
`SceneCollection` struct and associated versioning code. This was used
in very early 2.80 development period (up to 2.80 sub 14 apparently)
instead of the current 'master collection'.
The purpose of this commit is only to fix the crash, not to restore
the support for this old, deprecated and never-released type of data.