Problem with QTableWidget as input for QChart

[Huberti]

Hi, I would like to display points entered into table on the chart. The problem is that by default when cells are empty they are considered as points (0,0) on the chart. Here is code:

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

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);        
    ui->tableWidget->horizontalHeader()->setSectionResizeMode(QHeaderView::Stretch);
    ui->tableWidget->verticalHeader()->setSectionResizeMode(QHeaderView::Stretch);

    QChart* chart = new QChart();
    chart->legend()->hide();
    ui->chartView->setChart(chart);

    QLineSeries* series = new QLineSeries();

    QVXYModelMapper *mapper = new QVXYModelMapper(this);
    mapper->setXColumn(0);
    mapper->setYColumn(1);
    mapper->setSeries(series);
    mapper->setModel(ui->tableWidget->model());
    chart->addSeries(series);

    chart->createDefaultAxes();
}

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>579</width>
    <height>407</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>Chart</string>
  </property>
  <widget class="QWidget" name="centralWidget">
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
     <widget class="QChartView" name="chartView"/>
    </item>
    <item>
     <widget class="QTableWidget" name="tableWidget">
      <property name="rowCount">
       <number>5</number>
      </property>
      <property name="columnCount">
       <number>2</number>
      </property>
      <row/>
      <row/>
      <row/>
      <row/>
      <row/>
      <column>
       <property name="text">
        <string>x</string>
       </property>
      </column>
      <column>
       <property name="text">
        <string>y</string>
       </property>
      </column>
     </widget>
    </item>
   </layout>
  </widget>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <customwidgets>
  <customwidget>
   <class>QChartView</class>
   <extends>QGraphicsView</extends>
   <header>QtCharts</header>
  </customwidget>
 </customwidgets>
 <resources/>
 <connections/>
</ui>

Images how it looks like:
Empty table - there is unwanted (0, 0) point on the chart by default

Table with two points filled - unwanted point (0,0) causes bad results:

Is there any way to fix that?