When inserting item to Pie Chart, the legend entry is appended instead of being inserted too

When inserting an item to a pie chart, it is properly inserted to the index the user gives, but the legend item appended to the end instead of being inserted too.

Steps to reproduce:

• Run attached sample
• Click "Insert item" button
• EXPECTED: Item is inserted to index 2, and legend item is also inserted at index 2
• ACTUAL: Item is properly inserted, but legend item is appended to the end of the list