Program crashes after defining new role for model

I tried to implement a new model that sorts numerically as described here.

It looks like this:

#ifndef NUMERICMODEL_H
#define NUMERICMODEL_H

#include <QStandardItemModel>

class NumericModel : public QStandardItemModel
{
public:

    enum Role {
        SortRole=Qt::UserRole
    };

    NumericModel() {}
    ~NumericModel() {}

    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const {

        switch ( role ) {
            case Qt::DisplayRole:
                return index.data().toString();
            case SortRole:
                return index.data().toUInt();
            default:
                return index.data().toString();
        }

    }

};

#endif // NUMERICMODEL_H

I am setting the sort role like this:

QSortFilterProxyModel * proxyModel = new QSortFilterProxyModel(this);
proxyModel->setSourceModel(&m_movesModel);
proxyModel->setSortRole(NumericModel::SortRole);
qDebug() << __LINE__;
ui->tableView_Moves->setModel(proxyModel);qDebug() << __LINE__;
ui->tableView_Moves->resizeColumnsToContents();qDebug() << __LINE__;

However my program crashes in the last line, when calling ui->tableView_Moves->resizeColumnsToContents().