[14.0][FIX] utf-8 cached backup error auto_backup

[sergiocorato]

Error in backup process:

UnicodeDecodeError: 'utf-8' codec can't decode byte 0xeb in position 14: invalid continuation byte

How to replicate:

1. create one backup with filestore
2. create another backup without filestore
3. wait cron execution

Second error: the second backup is a copy of the first one, regardless of the type. So the second backup, of the type "dump", is a copy of the "zip" file without the correct extension.