Describe what you were doing when the bug occurred:
1. Clicking back to go back through the frames following a profile session. I think I got to zero and then clicked it again and then it errored

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DevTools version: 4.8.2-fed4ae024

Call stack: at getCommitTree (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:17661:26)
    at getCommitTree (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:17710:30)
    at getCommitTree (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:17710:30)
    at getCommitTree (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:17710:30)
    at getCommitTree (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:17710:30)
    at getCommitTree (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:17710:30)
    at getCommitTree (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:17710:30)
    at getCommitTree (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:17710:30)
    at getCommitTree (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:17710:30)
    at getCommitTree (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:17710:30)

Component stack: at CommitRankedAutoSizer (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:31963:48)
    at div
    at div
    at div
    at SettingsModalContextController (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:26139:23)
    at Profiler_Profiler (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:33363:48)
    at ErrorBoundary (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:27172:5)
    at PortaledContent (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:27303:32)
    at div
    at div
    at ProfilerContextController (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:30463:23)
    at TreeContextController (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:22538:23)
    at SettingsContextController (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:23040:27)
    at ModalDialogContextController (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:28328:23)
    at DevTools_DevTools (chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/main.js:33797:21)
const debug = (methodName, ...args) => {
  if (__DEBUG__) {
    console.log(
      `%cCommitTreeBuilder %c${methodName}`,
      'color: pink; font-weight: bold;',
      'font-weight: bold;',
      ...args,
    );
  }
};
const rootToCommitTreeMap: Map<number, Array<CommitTree>> = new Map();
export function getCommitTree({
  commitIndex,
  profilerStore,
  rootID,
}: {|
  commitIndex: number,
  profilerStore: ProfilerStore,
  rootID: number,
|}): CommitTree {
  if (!rootToCommitTreeMap.has(rootID)) {
    rootToCommitTreeMap.set(rootID, []);
  }
  const commitTrees = ((rootToCommitTreeMap.get(
    rootID,
  ): any): Array<CommitTree>);
  if (commitIndex < commitTrees.length) {
    return commitTrees[commitIndex];
  }
  const {profilingData} = profilerStore;