When selecting "Start Bitcoin Core on system login" in the settings, it will unselect itself after closing the dialog.

Tested with current master (e8ffec6) on Windows 7.

const QString &filter,
    QString *selectedSuffixOut)
{
    QString selectedFilter;
    QString myDir;
    if(dir.isEmpty()) 
    {
        myDir = QStandardPaths::writableLocation(QStandardPaths::DocumentsLocation);
    }
    else
    {
        myDir = dir;
    }
    
    QString result = QDir::toNativeSeparators(QFileDialog::getOpenFileName(parent, caption, myDir, filter, &selectedFilter));
    if(selectedSuffixOut)
    {
        
        QRegExp filter_re(".* \\(\\*\\.(.*)[ \\)]");
        QString selectedSuffix;
        if(filter_re.exactMatch(selectedFilter))
        {
            selectedSuffix = filter_re.cap(1);
        }
        *selectedSuffixOut = selectedSuffix;
    }
    return result;
}
Qt::ConnectionType blockingGUIThreadConnection()