Fix encrypted version to 0 when finding unencrypted file

Whenever the command is run and a "legacy cipher" seems to be detected
when the legacy option is disabled, it's highly likely that the file is
actually unencrypted but the database contains a encrypted version
higher than 0 for some reason.

The command now detects this case and automatically sets the encrypted
version to 0 so that the file can be read again.

Signed-off-by: Vincent Petry <vincent@nextcloud.com>