If there are no cached results the current implementation was also returning an empty array,
but this was the same as when there was a successful run.
So to distinguish this we return `null` if there are *no* results.
In this case we need to rerun the integrity checker.
Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>
Ferdinand Thiessen
Andy Scherzinger
Côme Chilliet