register_pointers causing a PHP Notice when on a page with no pointers

Line 82 reads:

``` PHP
$this->pointers = $pointers;
```

If there are no pointers set for the currently viewed page, this will show a PHP Notice that the variable $pointers is undefined.

This can be easily fixed by including $pointers = NULL; on line 61, right after the function starts. This way if there are no pointers, the variable will still be defined and thus no longer give the notice.
