I'm not sure how a .blend file could get into this state, but apparently
for some files saved with versions of Blender after the file browser
changes, the execute region would not have been created. File browser
code assumes this region to be there however.
Luckily I found a file with which I could recreate the issue. My guess
is that the error only happens with files that were stored before
certain versioning fixes were done after the file browser redesign.
To fix this, we just let the versioning code for the execute region run
even with newest files. We can run this safely, it only acts if the
execute region actually doesn't exist.
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