Update FilteredActionList.tsx

[mattcosta7]

Closes #

Fixes a crash in FilteredActionList where the virtualizer's getItemKey callback could be invoked with an index whose item was no longer present in items. @tanstack/react-virtual's measureElement can fire with a stale index after the list shrinks (e.g. while filtering), causing items[index] to be undefined and the subsequent item.key access to throw.

The callback now treats items[index] as possibly undefined and falls back to index.toString() as the key when the item has been removed.

Changelog

New

• N/A

Changed

• FilteredActionList: Guard against undefined entries in the virtualizer's getItemKey to prevent a runtime error when items are removed mid-render (e.g. during filtering).

Removed

• N/A

Rollout strategy

• Patch release
• Minor release
• Major release; if selected, include a written rollout or migration plan
• None; if selected, include a brief description as to why

Testing & Reviewing

• Open a story that renders FilteredActionList with virtualization enabled (e.g. the virtualized FilteredActionList story).
• Type into the filter input quickly so that items shrinks while the virtualizer is still measuring previously rendered rows.
• Before this change, this could throw Cannot read properties of undefined (reading 'key') from getItemKey. After this change, no error is thrown and the list re-renders with the filtered items.

Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Storybook)
• Changes are SSR compatible
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge
• (GitHub staff only) Integration tests pass at github/github-ui (Learn more about how to run integration tests)

[changeset-bot]

🦋 Changeset detected

Latest commit: 178214d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/react	Patch

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Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

⚠️ Action required

👋 Hi, this pull request contains changes to the source code that github/github-ui depends on. If you are GitHub staff, test these changes with github/github-ui using the integration workflow. Check the integration testing docs for step-by-step instructions. Or, apply the integration-tests: skipped manually label to skip these checks.

To publish a canary release for integration testing, apply the Canary Release label to this PR.

[Copilot]

Pull request overview

Fixes a runtime crash in FilteredActionList virtualization when @tanstack/react-virtual calls getItemKey with a stale index after the items array shrinks (e.g. during filtering), by handling items[index] being undefined.

Changes:

• Add a defensive guard in the virtualizer’s getItemKey to avoid reading .key from an undefined item and fall back to index.toString().
• Add a patch changeset documenting the crash fix.

Show a summary per file

File	Description
packages/react/src/FilteredActionList/FilteredActionList.tsx	Prevents a virtualization-related crash by guarding against stale indices in getItemKey.
.changeset/filtered-action-list-undefined-item-key.md	Adds a patch changeset describing the FilteredActionList crash fix.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 1