Linear Trendline not rendering correctly when aggregate sum is used

[yanmariomenev]

Description

The linear trendline doesn't render correctly when the aggregate sum is used for the series. The trendline renders downward, but it should render upward due to the positive values for each month.

Steps To Reproduce

Open the following example, which demonstrates a chart using the aggregate sum and a secondary chart where the values are aggregated without using the aggregate functionality of the chart. The top chart rendering is incorrect, as it should render as shown in the bottom chart.

Workaround

Use the sumOrNull aggregate.