Line 498 of WidgetRenderer.php from 2.6.3 BETA 12 doesn't seem to be that, so I'm assuming you haven't updated to the latest version.
But guessing from that single line only, it may have something to do with "Expression" option in widget setting. It's the option which lets you set custom expression for the widget. Something like, limiting it to certain usergroups, guests and whatnot. On a side note, since the beta version that feature appears to be deprecated and replaced by conditionals (that you can usually use in templates).