QLineEdit/QCompleter popup shows in top-level window

#include <QApplication>
#include <QLineEdit>
#include <QDialog>
#include <QVBoxLayout>
#include <QCompleter>
#include <QStandardItemModel>
#include <QIdentityProxyModel>

class AdaptiveFilterProxy : public QIdentityProxyModel
{
    Q_OBJECT
public:
    using QIdentityProxyModel::QIdentityProxyModel;

    static constexpr int SearchRole = 2000;

    void setText(const QString &text)
    {
        if (text == m_text)
            return;
        m_text = text;

        // This signal must be emitted to invalidate the completer, and force it to filter its rows again.

        emit dataChanged(index(0, 0), index(rowCount() - 1, 0), {SearchRole});
    }

    QVariant data(const QModelIndex &index, int role) const override
    {
        if (role != SearchRole)
            return QIdentityProxyModel::data(index, role);

        if (!m_text.isEmpty() && data(index, Qt::DisplayRole).toString().contains(m_text, Qt::CaseInsensitive)) {
            return m_text;
        } else {
            return "";
        }

        return QVariant();
    }

private:
    QString m_text;
};

int main(int argc, char**argv) {
    QApplication app(argc, argv);
    auto window = new QDialog;
    auto layout = new QVBoxLayout(window);

    auto lineEdit = new QLineEdit;
    layout->addWidget(lineEdit);

    auto model = new QStandardItemModel(window);
    model->appendRow(new QStandardItem("Hello"));
    model->appendRow(new QStandardItem("Hello 2"));
    model->appendRow(new QStandardItem("Hello 3"));

    auto completer = new QCompleter(window);
    lineEdit->setCompleter(completer);

    auto searchFilter = new AdaptiveFilterProxy(window);
    searchFilter->setSourceModel(model);

    QObject::connect(lineEdit, &QLineEdit::textChanged, searchFilter, &AdaptiveFilterProxy::setText);

    completer->setModel(searchFilter);
    completer->setFilterMode(Qt::MatchStartsWith);
    completer->setCompletionMode(QCompleter::PopupCompletion);
    completer->setCompletionRole(AdaptiveFilterProxy::SearchRole);

    window->show(); 

   return app.exec();
}

#include "main.moc"