Simplified version of the code which gives the same error:

Qt Code: 
  1. #include <QApplication>
  2. #include <QtCore>
  3. #include <QStandardItemModel>
  4. #include <QTableView>
  5. #include <QtGui>
  6.  
  7. using namespace std;
  8.  
  9. class MyObject {
  10.  
  11. };
  12.  
  13. Q_DECLARE_METATYPE(MyObject)
  14.  
  15.  
  16. class PaintDelegate : public QStyledItemDelegate {
  17.  
  18. public:
  19.     PaintDelegate(QWidget *parent = 0) : QStyledItemDelegate(parent) {}
  20.  
  21.     void paint(QPainter *painter, const QStyleOptionViewItem &option,
  22.                          const QModelIndex &index) const
  23.     {
  24.         if (qVariantCanConvert<MyObject>(index.data(Qt::UserRole + 1))) {
  25.             MyObject myObj = qVariantValue<MyObject>(index.data(Qt::UserRole + 1));
  26.         } else {
  27.             QStyledItemDelegate::paint(painter, option, index);
  28.         }
  29.     }
  30.  
  31. };
  32.  
  33. int main(int argc, char** argv)
  34. {
  35.     QApplication app( argc, argv );
  36.  
  38.     QStandardItem * item = new QStandardItem("item 1");
  39.     item->setData(qVariantFromValue(MyObject()));
  40.     model->setItem(0, 0, item);
  41.     QTableView * tableView2 = new QTableView();
  42.     tableView2->setModel(model);
  43.     tableView2->setItemDelegate(new PaintDelegate);
  44.     tableView2->show();
  45.  
  46.     extern void updateModel(QStandardItemModel*);
  47.     QtConcurrent::run(updateModel, model);
  48.  
  49.     return app.exec();
  50. }
  51.  
  52. void updateModel(QStandardItemModel* model){
  53.     for (;;){
  54.         model->item(0, 0)->setData(qVariantFromValue(MyObject()));
  55.     }
  56. }
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