God damn, I've recoded the code using isActive like that:
Qt Code: 
  1. void CMerchandizeBrowser::fillMerchandize(int groupId)
  2. {
  3.     qDebug() << "Entered CMerchandizeBrowser::fillMerchandize ...";    // debug
  4.     // sets up query string
  5.     QString queryString("SELECT * from merchandize WHERE GrupaIdentificationNumber=%1;");
  6.     //QString queryString("SELECT * from merchandize WHERE GrupaIdentificationNumber=2;");    // test
  7.     queryString=queryString.arg(groupId);
  8.     qDebug() << "Query: " << queryString;    // debug
  9.  
  10.     QSqlQuery query(queryString);    // sets up query from query string
  11.     removeAllMerchandize();    // removes all items
  12.     m_iImageCounter=0;    // inits counter
  13.     //query.exec(queryString);    // executes query string
  14.     // WARNING: Are we connected to database????
  15.     if (query.isActive())
  16.     {
  17.         while (query.next())
  18.         {
  19.             /*
  20.             if (groupId==query.value(iMerchandizeFieldGROUPID).toInt())
  21.             {
  22.             */
  23.                 QImage img(query.value(iMerchandizeFieldPICPATH).toString());    // fetches image from filename
  24.  
  25.                 tEmbeddImagesResult result=embeddedPicPath(img, query.value(iMerchandizeFieldPICPATH).toString());    // embedd pic path into pic
  26.                 if (result!=resFailue)
  27.                 {
  28.                     img=img.convertToFormat(QImage::Format_ARGB32_Premultiplied);
  29.                 }
  30.                 //addMerchandize(query.value(iMerchandizeFieldPICPATH).toString());    // adds merchandize pics
  31.                 setSlideCount(m_iImageCounter+1);
  32.                 setSlide(m_iImageCounter, img);
  33.                 m_iImageCounter++;
  34.             //}
  35.         }    // while
  36.     };
  37.     m_iSelected=m_iImageCounter / 2;    // sets selected pic
  38.  
  39.     //update();    // updates window
  40.     qDebug() << "m_iImageCounter: " << m_iImageCounter;    // debug
  41.     qDebug() << "m_iSelected: " << m_iSelected;    // debug
  42.     qDebug() << "Exiting CMerchandizeBrowser::fillMerchandize ...";    // debug
  43. }
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and isActive under if skips while loop. Thas means I am not connected to database??