It works once, but crashes if I do it again

I call this code on the startup of the application, but if I call it again, it crashes without any errors.

Code:

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void MCM::repopWList()
{
    QDir mcDir = QDir(McFolder);
    QDir backupsDir = QDir(McFolder);
    mcDir.cd("saves");
    backupsDir.cd("MCM/backups");
    mcDir.setFilter(QDir::Dirs | QDir::NoDotAndDotDot);
    backupsDir.setFilter(QDir::Dirs | QDir::NoDotAndDotDot);
 
    ui->worldList->clear();
 
    //list the worlds
    QFileInfoList mcDirList = mcDir.entryInfoList();
    for (int i = 0; i < mcDirList.size(); i++) {
        QFileInfo fileInfo = mcDirList.at(i);
        ui->worldList->addItem(fileInfo.fileName());
    }
    QFileInfoList backupsDirList = backupsDir.entryInfoList();
    for (int i = 0; i < backupsDirList.size(); i++)
    {
        bool wExist = false;
        QFileInfo backupInfo = backupsDirList.at(i);
        for (int j = 0; j < ui->worldList->count(); j++)
        {
            string itemText = ui->worldList->item(j)->text().toStdString();
            if (itemText == backupInfo.fileName().toStdString())
            {
                wExist = true;
            }
        }
        if (wExist == false)
        {
            QString newWorld(backupInfo.fileName());
            ui->worldList->addItem(newWorld);
        }
    }
}

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Have you run it in your debugger and looked at the backtrace you get when it crashes? What line causes the crash?

I get EXC_BAD_ACCESS

caused by

Code:

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ui->worldList->clear()

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Is ui->worldList a valid pointer? Have you deleted (or called deleteLater()) on the list at any time? Does any other part of your program hold a pointer to any QListWidgetItem in the list?