### 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
```
TOD
      
       Cal
      primaryFibers.delete(primaryFiber);
      return;
    }
    const id = getFiberID(primaryFiber);
    if (isRoot) {
       Roo
       So 
      pendingUnmountedRootID = id;
    } else if (!shouldFilterFiber(fiber)) {
       To 
       we'
       and 
      if (isSimulated) {
        pendingSimulatedUnmountedIDs.push(id);
      } else {
        pendingRealUnmountedIDs.push(id);
      }
    }
    fiberToIDMap.delete(primaryFiber);
    idToFiberMap.delete(id);
    primaryFibers.delete(primaryFiber);
    const isProfilingSupported = fiber.hasOwnProperty('treeBaseDuration');
    if (isProfilingSupported) {
      idToRootMap.delete(id);
      idToTreeBaseDurationMap.delete(id);
    }