from_ab() raises InvalidAndroidBackup instead of exiting when it runs as a
sub-command, which check-androidqf catches to skip the backup modules. The
two password branches still called sys.exit(1) unconditionally, and since
run_backup_cmd() runs inside finish(), that ended the parent run before the
intrusion-logs command and before the timeline, alerts, urls, info and run
manifest were stored — leaving an output directory that looks complete but
has no alerts.json.
Also drop "as backup.ab is malformed" from the skip warning: it covers a
missing or wrong password too.
