"Cancel" should either remove the partial snapshot or list it in the UI

[s-h-a-d-o-w]

Is your feature request related to a problem? Please describe.
When cancelling snapshot creation, files are left on the disk. Users wouldn't know, unless they check the snapshot directory.

Describe the solution you'd like
Simply remove the partially created snapshot on cancel.

Describe alternatives you've considered
List the partial snapshot in the UI somehow. This seems unnecessarily complex though.

[FrostBird347]

Incomplete snapshots are automatically removed upon the next scheduled backup (which is run once an hour regardless of the user's scheduled backup settings), but that's unlikely to happen with users who only briefly plug in the backup disk to make a manual backup via the GUI, so I do agree that snapshots should be also cleaned up after a user clicks cancel.