QComboBoxListView display misalignment after sliding

[Code]

#include <QComboBox>
#include <QScroller>
#include <QAbstractItemView>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    QComboBox *comboBox = new QComboBox(this);
    for (int i = 0; i < 60; i++) {
        comboBox->addItem(" item " + QString::number(i + 1));
    }
    QScroller::grabGesture(comboBox->view(), QScroller::LeftMouseButtonGesture);
}

[Steps]

1.Click the QComboBox component and scroll the mouse to hide a part of the item above;

2.At this moment, press the left mouse button and drag the QComboBoxListView down;

3.Release the left mouse button, QComboBoxListView will automatically return to position;

4.But the position has been misplaced, and there is a blank underneath;

5.On the contrary, if you drag upwards, there will be a blank space above.

[Hope]

I hope that there will be no blank space on the top or bottom after the scrolling is over