Bad html class attribute in commons_groups_preprocess_node()

In commons_groups_preprocess_node(), the user's picture has a class added to it like this:

'attributes' => array(
  'title' => t("View @user's profile.", array('@user' => format_username($account))),
  'class' => 'user-picture',
),

This is incorrect however - class should be an array. If anything tries to add to that class later by pushing an item onto the array, you get a fatal error since it is a string...