title: Problem with dynamically updating a QLineSeries
body: <p>I encounter a problem when I try to make a self updating  QLineSeries through the help of QThread.</p>
  <pre><code>from PySide2.QtCore import *
  from PySide2 import *
  from PySide2.QtWidgets import *
  from PySide2.QtCharts import *
  from PySide2.QtGui import *
  
  import time
  
  
  baseValuesList = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
  
  randomValuesList = [256, 14, 89, 100, 150, 500, 50, 34, 67, 90, 102, 12, 19, 89, 34, 145, 71, 4, 89, 47]
  
  rangeList = list(range(len(baseValuesList))) 
  
  def listUpdatingFunction(): 
      baseValuesList.pop(0)
      baseValuesList.append(randomValuesList[0])
      randomValuesList.pop(0)
  
  class Worker(QObject):
      def __init__(self, function, interval):
          super(Worker, self).__init__()
          self._step = 0
          self._isRunning = True
          self.function = function
          self.interval = interval
  
      def task(self):
          if not self._isRunning:
              self._isRunning = True
              self._step = 0
  
          while self._isRunning == True:
              self.function()
              time.sleep(self.interval)
  
      def stop(self):
          self._isRunning = False
          
  class minimalMonitor(QtWidgets.QWidget):
      def __init__(self):
          QtWidgets.QWidget.__init__(self)
            
          # Creating QChart
          self.layout = QVBoxLayout()
          self.setLayout(self.layout)
          self.chart = QtCharts.QChart()
          self.chart.setAnimationOptions(QtCharts.QChart.AllAnimations)
          self.series = QtCharts.QLineSeries()
          for i in rangeList:
              self.series.append(i,baseValuesList[i])
          self.chart.addSeries(self.series)
          self.chart_view = QtCharts.QChartView(self.chart)
          self.chart_view.setRenderHint(QPainter.Antialiasing)
          self.layout.addWidget(self.chart_view)
          self.axis_x = QtCharts.QValueAxis()
          self.chart.addAxis(self.axis_x, Qt.AlignBottom)
          self.axis_y = QtCharts.QValueAxis()
          self.chart.addAxis(self.axis_y, Qt.AlignLeft)
          self.axis_x.setRange(0, 20)
          self.axis_y.setRange(0, 300)
          self.series.attachAxis(self.axis_x)
          self.series.attachAxis(self.axis_y)
          self.thread = QThread()
          self.thread.start()
  
          self.worker = Worker(self.update, 1)
          self.worker.moveToThread(self.thread)
  
          self.autoUpdateStart = QPushButton(&quot;Start Auto-Update&quot;)
          self.autoUpdateStart.setCheckable(False)
          self.autoUpdateStart.toggle()
          self.autoUpdateStart.clicked.connect(self.worker.task)
          
          self.autoUpdateStop = QPushButton(&quot;Stop Auto-Update&quot;)
          self.autoUpdateStop.setCheckable(False)
          self.autoUpdateStop.toggle()
          self.autoUpdateStop.clicked.connect(lambda: self.worker.stop())
          self.layout.addWidget(self.autoUpdateStart)
          self.layout.addWidget(self.autoUpdateStop)
          self.manualUpdateButton = QPushButton(&quot;Manual Update&quot;)
          self.manualUpdateButton.setCheckable(False)
          self.manualUpdateButton.toggle()
          self.manualUpdateButton.clicked.connect(self.update)
          self.layout.addWidget(self.manualUpdateButton)
      def update(self):
              listUpdatingFunction()
              self.series.clear()
  
              for i in rangeList:
                  self.series.append(i,baseValuesList[i])
  
              self.chart_view.update()
              
  if __name__ == '__main__':
      import sys
      app = QtWidgets.QApplication(sys.argv)
      widget = minimalMonitor()
      widget.show()
      sys.exit(app.exec_())
  </code></pre>
  <p>In a nutshell, if I call directly the update function or press manual update, the QLineSeries will correctly append, but as soon as I use the QThread or Auto Update button it goes haywire and will always try to join with the Axis Origin.
  Does any one have an idea why it is doing this?</p>