Callout Example has a strange artifact on the left hand side when you click the series

The callout example has a strange artifact on the left hand side when you click the series.  The artifact is not easily discovered. You should change the axisX and axisY to the range [-1, 10] by using : 

m_chart->axisY()->setRange(-1, 10);

m_chart->axisX()->setRange(-1, 10);

Then when you click the any series on the window, the artifact will display at the same time.

One way to solved this bug is to add a code at keepCallout method.

After modification, the keepCallout method is 

void View::keepCallout()

{          m_callouts.append(m_tooltip);            m_tooltip = new Callout(m_chart);          m_tooltip->hide();//This is the code line I added }

But I am not sure it is the best way to solve this problem. Thx.