### Issue Details

* **Electron Version:**
  * 13.0.0-nightly.20201203
* **Operating System:**
  * macOS
* **Last Known Working Electron version:**
  * N/A

### Expected Behavior
`WebFrameMain.frames` should never contain undefined

### Actual Behavior
```
Uncaught Exception:
TypeError: Cannot read property 'processId' of undefined
    at id (/private/var/folders/_7/jm5cr84j7jd4v7btf2d3bqwm0000gn/T/tmp-59557-p4DTr3KWOsNk/main.js:4:38)
    at pft (/private/var/folders/_7/jm5cr84j7jd4v7btf2d3bqwm0000gn/T/tmp-59557-p4DTr3KWOsNk/main.js:6:36)
    at Timeout._onTimeout (/private/var/folders/_7/jm5cr84j7jd4v7btf2d3bqwm0000gn/T/tmp-59557-p4DTr3KWOsNk/main.js:27:5)
    at listOnTimeout (internal/timers.js:554:17)
    at processTimers (internal/timers.js:497:7)
```

### To Reproduce
Run https://gist.github.com/f46823470955034b4a456b6275862bfb for a short while and you'll observe the above error.

cc @samuelmaddock 

shell/browser/api/electron_api_web_frame_main.cc
auto* web_frame = FromRenderFrameHost(rfh);
  if (web_frame)
    web_frame->MarkRenderFrameDisposed();
}
v8::Local<v8::ObjectTemplate> WebFrameMain::FillObjectTemplate(
    v8::Isolate* isolate,
    v8::Local<v8::ObjectTemplate> templ) {
  return gin_helper::ObjectTemplateBuilder(isolate, templ)
      .SetMethod("executeJavaScript", &WebFrameMain::ExecuteJavaScript)
      .SetMethod("executeJavaScriptInIsolatedWorld",
                 &WebFrameMain::ExecuteJavaScriptInIsolatedWorld)
      .SetMethod("reload", &WebFrameMain::Reload)
      .SetMethod("_send", &WebFrameMain::Send)
      .SetMethod("_postMessage", &WebFrameMain::PostMessage)
      .SetProperty("frameTreeNodeId", &WebFrameMain::FrameTreeNodeID)
      .SetProperty("name", &WebFrameMain::Name)
      .SetProperty("osProcessId", &WebFrameMain::OSProcessID)
      .SetProperty("processId", &WebFrameMain::ProcessID)
      .SetProperty("routingId", &WebFrameMain::RoutingID)
      .SetProperty("url", &WebFrameMain::URL)
      .SetProperty("top", &WebFrameMain::Top)
      .SetProperty("parent", &WebFrameMain::Parent)
      .SetProperty("frames", &WebFrameMain::Frames)
      .SetProperty("framesInSubtree", &WebFrameMain::FramesInSubtree)
      .Build();
}
const char* WebFrameMain::GetTypeName() {