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.