In this [issue](https://github.com/facebook/react/issues/23373), when you navigate to [this app](https://next-rsc-notes.vercel.app/note/1646289027680) and inspect the sidebar in the components tab, you will get this error:

![image](https://user-images.githubusercontent.com/2735514/158241727-64eba8f9-5ac2-4aa7-bffa-ff9b3174a261.png)

 This is a user error. One of the components in the user's app thrown. However, the UI for this is confusing, because it seems like it's a DevTools error. We've gotten a lot of bug reports like this, and it would be good to differentiate between DevTools bugs and bugs in the app. For this task:

- [ ] Build the React DevTools extension locally (instructions [here](https://github.com/facebook/react/tree/main/packages/react-devtools-extensions)) and reproduce the error
- [ ] Figure out a way to have the front end be able to differentiate whether the error is a error within DevTools or within the user's app
- [ ] Design/implement a better UI to help app developers distinguish between these two cases
BEGIN copied code
  function findCurrentFiberUsingSlowPathById(id: number): Fiber | null {
    const fiber = idToArbitraryFiberMap.get(id);
    if (fiber == null) {
      console.warn(`Could not find Fiber with id "${id}"`);
      return null;
    }
    const alternate = fiber.alternate;
    if (!alternate) {
       I
      const nearestMounted = getNearestMountedFiber(fiber);
      if (nearestMounted === null) {
        throw new Error('Unable to find node on an unmounted component.');
      }
      if (nearestMounted !== fiber) {
        return null;
      }
      return fiber;
    }
     I
     t
     s
    let a: Fiber = fiber;
    let b: Fiber = alternate;
    while (true) {
      const parentA = a.return;
      if (parentA === null) {
         W
        break;
      }