Get root id from url always fails.

There is a rather big bug in the Method: `Frontend::getRootIdFromUrl()` which prevents it from working entirely.

The method consists of:
```php
$objRootPage = static::getRootPageFromUrl();
return $objRootPage->numRows ? $objRootPage->id : 0;
```
There is one bug and one quirk as `Frontend::getRootPageFromUrl()`:
1. does only return a Model instance and no collection or Database result (the bug).
2. does a redirect or 404 effectively always killing the script when no root page has been found and therefore the check if there was a root page returned is entirely obsolete (the quirk).