[REG: 5.8->5.9]: Removing the data from a QBarSet without removing the barset itself from a QStackedBarSeries, it leaves the removed data labels to the chart

When removing the data from a QBarSet without removing the QBarSet from QStackedBarSeries itself, the removed data's labels are left in the chart.

This is regression from 5.8 to 5.9, caused by the optimization code done for issue QTBUG-52442

Steps to reproduce:

• Run attached sample
• Press "delete barset2" button, which removes the data from the barset2
• EXPECTED: All references to the removed data is removed
• ACTUAL: Labels in the chart are left in place while the bars themselves are updated