Index doesn't show up in frameset and table

If I set 

```
    define('ABBRV_TYPE','index');
    define('BIBTEXBROWSER_LAYOUT','table');
    bibtexbrowser_configure('BIBTEXBROWSER_DEFAULT_DISPLAY','PagedDisplay');
```

then the bibtex entries do not have indexes in front of them. It only shows a pair of empty brackets. Is this related to the `getRawAbbv()` function?

Thanks,
Qi
