914f4308fb
When reading a old .blend file (from before the new file browser design), we wouldn't create the execute region for existing file editors. This usually wasn't an issue, but it could become one when a file browser was opened in a temporary screen before, and that screen was still visible. Then code spawning the new file browser would re-use the old file browser data, assuming the execute region was there. Handle this in versioning code and let rest of the code keep sane assumtions (e.g. that there always is a execute region, even if invisible).