سوال: خطا در tableWidget

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
ui->tableWidget->setColumnCount(3);
ui->tableWidget->setRowCount(3);
ui->tableWidget->resizeColumnsToContents();
}

MainWindow::~MainWindow()
{
delete ui;
}

void MainWindow::on_pushButton_clicked()
{
if(ui->tableWidget->item(0,0)->text().isEmpty())
ui->label->setText("empty");
else
ui->label->setText("full");
}