Blender Git Loki

Fix failing asserts in versioning with some pre 2.5 files

Old pre 2.5 files may have had non active spaces stored that doen't have
a header. The 2.5 versioning only added headers for active spaces, not
inactive (so invisible) ones.
Newer versioning code assumed there to always be a header though.

Inserted a version patch to make sure there's always a header now.

Fixes error reported to Debian,
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=949035.