Форум

$arResult['AUTHORS'] = [];

foreach($arResult['ITEMS'] as $arItem)
{
   $id = (int) $arItem['PROPERTIES']['AVTOR']['VALUE'];

   if ( $id > 0 )
   {
      $arResult['AUTHORS'][$id] = $id;
   }
}

if ( !empty($arResult['AUTHORS']) )
{
   $authors = \Bitrix\Iblock\ElementTable::getList([
      'select' => [
         'ID',
         'NAME',
         'PREVIEW_PICTURE'
      ],
      'filter' => [
         'IBLOCK_ID' => XX,
         'ID'        => $arResult['AUTHORS'],
         'ACTIVE'    => 'Y'
      ]
   ]);

   foreach( $authors as $author )
   {
      $arResult['AUTHORS'][ $author['ID'] ] = [
         'ID' => $author['ID'],
         'NAME' => $author['NAME'],
         'PREVIEW_PICTURE' => $author['PREVIEW_PICTURE'],
      ];
   }
}

CSaleBasket::DeleteAll($ar_res["ID"], false);

"   AND f.USER_ID is null ".