### 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.h
static gin::Handle<WebFrameMain> FromID(v8::Isolate* isolate,
                                          int render_process_id,
                                          int render_frame_id);
  static gin::Handle<WebFrameMain> From(
      v8::Isolate* isolate,
      content::RenderFrameHost* render_frame_host);
  
  
  static void RenderFrameDeleted(content::RenderFrameHost* rfh);
  
  
  void MarkRenderFrameDisposed();
  
  static gin::WrapperInfo kWrapperInfo;
  static v8::Local<v8::ObjectTemplate> FillObjectTemplate(
      v8::Isolate*,
      v8::Local<v8::ObjectTemplate>);
  const char* GetTypeName() override;
 protected:
  explicit WebFrameMain(content::RenderFrameHost* render_frame);
  ~WebFrameMain() override;
 private:
  
  
  bool CheckRenderFrame() const;
  v8::Local<v8::Promise> ExecuteJavaScript(gin::Arguments* args,
                                           const base::string16& code);
  v8::Local<v8::Promise> ExecuteJavaScriptInIsolatedWorld(
      gin::Arguments* args,
      int world_id,