[Bug] a valid backup can get replaced by an empty 0kb backup when scheduled backup fails to complete

[guitarjorge24]

Description
I have NeoBackup set to keep a max of 2 backup revisions per app.
If I lose root due to an OS update, my scheduled daily backup will fail (as expected) and then one my previous valid backups that were made when I still had root access wil get replaced by a new empty backup that is zero bytes (an empty folder).

Steps To Reproduce

1. Set the max backup revisions to 2
2. Create 2 backup revisions for an app with a phone that has root access
3. Create a schedule that makes a daily backup of the app you chose.
4. Remove root access from the phone
5. Wait for the daily schedule to run again.
6. The backup from the daily schedule will fail due to not having root access and one of the 2 valid/working backups will get replaced by an invalid backup (i.e. an empty folder).

Expected behavior
If the backup fails, then I would expect it to NOT replace one of my valid backup revisions.
Also, the scheduled backup maybe should not even try to run if the phone no longer has root access.
Otherwise, I would expect to have an option to not replace backup revisions with a new backup if the newer backup fails to complete.

System Information(please complete the following information):

• Device: Xioami Mi 12 Pro
• Android Version: 13
• ROM: MIUI 14.0.15
• App's Version: 8.3.4 (I also tried 8.3.2)

[guitarjorge24]

Additional Notes:

• I first found the issue in Neo Backup version 8.3.2 and then updated to 8.3.4 but the issue still occurred.
• The use case for this issue is that sometimes I remove root access from my phone so that certain apps work (e.g. a game that terminates itself when it detects the phone is rooted)

[Dogora]

Confirmed with my Pixel 4a (sunfish) running LineageOS 21.0, F-Droid build 8.3.10.

While playing around because of issue 933 I tried denying root to Neo Backup. The app presented a screen about requiring root (expected), but the schedule run-away started anyway. Multiple empty backups were then created and useful ones were deleted before I could force-stop the app.

Seems to me that if root is not granted, schedules should not run.