Issue: Undefined Index: user_group_id when merging users

protected function _postDelete()

	protected function _preDelete()
	{
		// make sure the deleted user is stored for postDelete
		$user = vw_Hard_Core::controller('Fetch')->get('User', $this->get('user_id'));

		parent::_preDelete();
	}

		parent::_postDelete();

		$user = array('userid' => $this->get('user_id'));

		$user = vw_Hard_Core::controller('Fetch')->get('User', $this->get('user_id'));

		if (!$user)
		{
			$user = array('userid' => $this->get('user_id'));
		}

		parent::_postDelete();

		if ($newUserId === null)
		{
			vw_Hard_Core::model('Plugins/Data')->do_user_name($newUserName, array(
				'userid' => $existingUserId,
				'username' => $oldUserName
			));
		}
		else
		{
			vw_Hard_Core::model('Plugins/Data')->do_user_merge(
				array(
					'userid' => $existingUserId,
					'username' => $oldUserName
				),
				array(
					'userid' => $newUserId,
					'username' => $newUserName
				)
			);
		}

		if ($newUserId === null)
		{
			$olduser = vw_Hard_Core::controller('Fetch')->get('User', $existingUserId);

			if ($olduser)
			{
				// only do this if the user wasn't deleted before we got here
				vw_Hard_Core::model('Plugins/Data')->do_user_name($newUserName, array(
					'username' => $oldUserName
				) + $olduser);
			}
		}
		else
		{
			$userids = array($existingUserId);

			if ($newUserId)
			{
				$userids[] = $newUserId;
			}

			$users = vw_Hard_Core::controller('Fetch')->get('User', $userids);

			if (!$newUserId)
			{
				$users[0] = array(
					'user_id' => 0,
					'userid' => 0,
					'user_group_id' => VW_GUEST_GROUP,
					'usergroupid' => VW_GUEST_GROUP
				);
			}

			if ($users["$existingUserId"] AND $users["$newUserId"])
			{
				// make sure none of these users was deleted while the merge was happening
				vw_Hard_Core::model('Plugins/Data')->do_user_merge(
					array(
						'username' => $oldUserName
					) + $users["$existingUserId"],
					array(
						'username' => $newUserName
					) + $users["$newUserId"]
				);
			}
		}

Fatal error: Unsupported operand types in /home/community/library/vw/XenForo/Model/User.php on line 132

ErrorException: Fatal Error: Unsupported operand types - library/vw/XenForo/Model/User.php:132

array(3) {
  ["url"] => string(64) "http://community.adeptgamer.com/admin.php?users/moderated/update"
  ["_GET"] => array(1) {
    ["users/moderated/update"] => string(0) ""
  }
  ["_POST"] => array(2) {
    ["users"] => array(1) {
      [1950] => array(2) {
        ["action"] => string(6) "reject"
        ["reject_reason"] => string(0) ""
      }
    }
    ["_xfToken"] => string(8) "********"
  }
}

array(3) {
  ["url"] => string(67) "http://community.adeptgamer.com/admin.php?users/ugecoha.1950/delete"
  ["_GET"] => array(1) {
    ["users/ugecoha_1950/delete"] => string(0) ""
  }
  ["_POST"] => array(2) {
    ["_xfConfirm"] => string(1) "1"
    ["_xfToken"] => string(8) "********"
  }
}

array(3) {
  ["url"] => string(64) "http://community.adeptgamer.com/admin.php?users/larka.1557/merge"
  ["_GET"] => array(1) {
    ["users/larka_1557/merge"] => string(0) ""
  }
  ["_POST"] => array(3) {
    ["username"] => string(7) "Yuuyake"
    ["_xfConfirm"] => string(1) "1"
    ["_xfToken"] => string(8) "********"
  }
}