BarSets should not be deleted in barseries

auto s1 = new QBarSet("Set 1", m_series);
auto s2 = new QBarSet("Set 2", m_series2);    m_series->append(s1);
m_series2->append(s2);
m_series->replace(s1, s2);
m_series2->replace(s2, s1);