Qt Assistant as Custom Help Viewer

[UVV]

Hi,
I use Qt Assistant as Custom Help Viewer.
I call it from my application like in the example:

...
   if (!proc)
      proc = new QProcess();
 
   if (proc->state() != QProcess::Running) {
      QString app = QCoreApplication::applicationDirPath() +
                    QDir::separator();
#if !defined(Q_OS_MAC)
      app += QLatin1String("assistant");
#else
      app += QLatin1String("Assistant.app/Contents/MacOS/Assistant");
#endif
 
      QStringList args;
      args << QLatin1String("-collectionFile")
            << QCoreApplication::applicationDirPath()
            + QDir::separator()
            + QLatin1String("helpfile.qhc")
            << QLatin1String("-enableRemoteControl");
 
      proc->start(app, args);
   ...

...
   if (!proc)
      proc = new QProcess();

   if (proc->state() != QProcess::Running) {
      QString app = QCoreApplication::applicationDirPath() +
                    QDir::separator();
#if !defined(Q_OS_MAC)
      app += QLatin1String("assistant");
#else
      app += QLatin1String("Assistant.app/Contents/MacOS/Assistant");
#endif

      QStringList args;
      args << QLatin1String("-collectionFile")
            << QCoreApplication::applicationDirPath()
            + QDir::separator()
            + QLatin1String("helpfile.qhc")
            << QLatin1String("-enableRemoteControl");

      proc->start(app, args);
   ...

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If I don't close a documentation tab in the Assistant, i.e. just close the Assistant, and then use my Help button several times in a row I've got several empty tabs like in an attached image.
How can I get rid of it?
Thanks in advance.