Bar chart with two dataSets throws exception when re rendered

One of my ViewControllers has a BarChart with two dataSets. It works fine when loaded first time. But if I navigate to some other page and come back, it gets re rendered. At that point it throws index out of bound error in prepareBuffer() function at buffer = _buffers[index] line.

I am not sure why it works first time and fails on re-rendering

Start by reproducing the BarChart lifecycle with two dataSets, navigating away, and returning to trigger the re-render. Inspect prepareBuffer(), especially the buffer = _buffers[index] access, and trace how buffers are initialized or reused between renders. Done means the chart can be re-rendered without an index-out-of-bounds exception.

Written by the indexing model from the issue text.