Unsolved QSqlRelationalTableModel fail update

[Jukov]

My db
personnelModel = new QSqlRelationalTableModel(this,db);
personnelModel->setTable("Personnel");
currentModel = operationModel;
currentModel->setRelation(currentModel->fieldIndex("Articul_idArticul"),QSqlRelation("Articul", "idArticul", "Number"));
// qDebug()<<currentModel->lastError()<<currentModel->query().lastQuery();
currentModel->setEditStrategy(QSqlRelationalTableModel::OnFieldChange);
currentModel->select();
ui->tableView->setModel(currentModel);The data is correctly displayed.
Qt does not issue errors.
After selecting in the combobox, the value is not updated, I looked up the database logs and saw it
Why does "is null" appear?

[Jukov]

I found this code in qsqldriver.cpp.

case WhereStatement:
   {
       const QString tableNamePrefix = tableName.isEmpty()
           ? QString()
           : prepareIdentifier(tableName, QSqlDriver::TableName, this) + QLatin1Char('.');
       for (int i = 0; i < rec.count(); ++i) {
           if (!rec.isGenerated(i))
               continue;
           s.append(s.isEmpty() ? QLatin1String("WHERE ") : QLatin1String(" AND "));
           s.append(tableNamePrefix);
           s.append(prepareIdentifier(rec.fieldName(i), QSqlDriver::FieldName, this));
           if (rec.isNull(i))
               s.append(QLatin1String(" IS NULL"));
           else if (preparedStatement)
               s.append(QLatin1String(" = ?"));
           else
               s.append(QLatin1String(" = ")).append(formatValue(rec.field(i)));
       }
       break;
   }

"IS NULL" appears from the fact that QSqlRecord &rec is null, but when i get record from model it returned normal record