When attempting to do a rollback on versions, the installer will not restart

# Describe the bug

A common way to force a re-upgrade from the GUI, is by resetting the Cacti version to a lower version via the database using the syntax below:

```sql
UPDATE version SET cacti='some_previous_version';
```

When you do this, the GUI upgrade will not work properly and you get locked out of Cacti.

## Expected behavior

Cacti should be easy to use.