### Describe what you were doing when the bug occurred:
1. I did profiling on a list, that gets updated on each pagination api call.
2. Once the profiling was done, I moved around in the Profiler to view the Flamegraph
3. Moving to second capture, the Profiler crashed.


**DevTools version**: 4.6.0-6cceaeb67

```
Component stack: in ec
    in div
    in div
    in div
    in So
    in Unknown
    in n
    in Unknown
    in div
    in div
    in rl
    in Ze
    in fn
    in Ga
    in _s
```
const MOUNTING = 1;
  const MOUNTED = 2;
  const UNMOUNTED = 3;
   This function is copied from React and should be kept in sync:
   https:github.com/facebook/react/blob/master/packages/react-reconciler/src/ReactFiberTreeReflection.js
  function isFiberMountedImpl(fiber: Fiber): number {
    let node = fiber;
    let prevNode = null;
    if (!fiber.alternate) {
       If 
       yet
      if ((getFiberFlags(node) & Placement) !== NoFlags) {
        return MOUNTING;
      }
       Thi
      if ((getFiberFlags(node) & Incomplete) !== NoFlags) {
        return UNMOUNTED;
      }
      while (node.return) {
        prevNode = node;
        node = node.return;
        if ((getFiberFlags(node) & Placement) !== NoFlags) {
          return MOUNTING;
        }
         Thi
        if ((getFiberFlags(node) & Incomplete) !== NoFlags) {
          return UNMOUNTED;
        }
         If 
        const isTimedOutSuspense =