VBO group field not shown

With views 6.x-2.8, the grouping field does not show up when set. Multiple views show up as appropriate for the groups, but the name of each group fails to show.

There was recently a similar issue in views itself that was marked resolved: #619884: Grouping does not work - using grid style, Row style: Fields. From a quick glance, the fixes were for the views_plugin_style class.

Reporting this as a VBO bug, as the other types work fine with grouping.