Incrementally updating data where value has become null does not update the column (it remains with old data)

[cheryllaird]

Bug description
I have a chart which shows Jan, Feb and March.

On initial load, March is null. As the initial load uses setAll this all seems to display as expected, Jan and Feb are populated and there is an empty column for March as the data is null.

When updating the data, Feb becomes null and March is populated. I am doing an incremental update via setIndex. March populates as expected but February does not update and the column remains with the old data.

I do not want to use removeIndex on the update as this will also remove the February column space on the chart.

https://codepen.io/cheryllaird/pen/YzmgGbV?editors=1010