Fix undefined index and consequential damages in versions code

Fix undefined index and consequential damages in versions code

If the user has no space and there are no versions, there won't be an
`all` index in the versions entry. Hence this triggers a warning and
becomes `null`, afterwards `count`, `foreach` and friends will happily
throw even more warnings and errors because they don't want to play with
`null`. Thus adding a fallback to an empty array.

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>