fix: handle undefined series during re-renders

[ryugaraj]

Description

Charts crashing when tooltip is visible and any kind of re-renders happen (updating timerange, zooming in, resizing chart, etc).

Ideally tooltips should immediately hide onMouseLeave but sometimes they stay visible and any kind of interaction with the chart causes the chart to crash.

This issue can be reproduced easily by disabling onMouseLeave on the tooltip in core-chart.

The main cause behind the issue was series being undefined and trying to access series.chart causing the crash.

Screen.Recording.2025-12-22.at.18.27.19.mov

How has this been tested?

Tested in Core chart and CloudWatch console.

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[jperals]

Not blocking, but why not instead add a question mark here after series?

const chart = group[0]?.series?.chart;

Then adding the previous check is not necessary.

[ryugaraj]

It's just to be explicit here, we had similar issues in the past with core-chart and we went with similar approach of handling it explicitly.

[jperals]

Any change a test can be added, or the issue cannot be reproduced reliably?

[ryugaraj]

Any change a test can be added, or the issue cannot be reproduced reliably?

Unfortunately, it's happening intermittently. But I can try following up with a case that helps up replicate every time and can add a test for it.