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### Issue Details
`webContents.openDevTools();` produces error:
`[12703:1102/100312.745262:ERROR:CONSOLE(1)] "Uncaught TypeError: Cannot read property 'setDockSide' of undefined", source: devtools://devtools/bundled/devtools_app.html?remoteBase=https://chrome-devtools-frontend.appspot.com/serve_file/@1eb8474cd7e4fccfbfa8048eceda1eab8b4d394/&can_dock=true&toolbarColor=rgba(223,223,223,1)&textColor=rgba(0,0,0,1)&experiments=true (1)`

Opening dev tools via these methods also produces the same error:
* Right click background > Inspect element
* Ctrl-Shift-I

* **Electron Version:**
  * 11.0.0-beta.18
* **Operating System:**
  * Debian 10 Buster x64, KDE Plasma
* **Last Known Working Electron version:**
  * 10.1.4

### Expected Behavior
Dev tools should open without error.

### Actual Behavior
Above error appears in the terminal.

### To Reproduce
Running this code will probably do it, although I'm opening a URL, but that shouldn't matter.
https://www.electronjs.org/docs/tutorial/quick-start#create-a-basic-application

### Additional Information
I need the beta because the stable version's node is too old.
shell/browser/ui/inspectable_web_contents.cc
web_contents_(web_contents),
      is_guest_(is_guest),
      view_(CreateInspectableContentsView(this)),
      weak_factory_(this) {
  const base::Value* bounds_dict = pref_service_->Get(kDevToolsBoundsPref);
  if (bounds_dict->is_dict()) {
    devtools_bounds_ = DictionaryToRect(bounds_dict);
    
    if (devtools_bounds_.height() < 100 || devtools_bounds_.width() < 100) {
      devtools_bounds_.set_height(600);
      devtools_bounds_.set_width(800);
    }
    if (!IsPointInScreen(devtools_bounds_.origin())) {
      gfx::Rect display;
      if (!is_guest && web_contents->GetNativeView()) {
        display = display::Screen::GetScreen()
                      ->GetDisplayNearestView(web_contents->GetNativeView())
                      .bounds();
      } else {
        display = display::Screen::GetScreen()->GetPrimaryDisplay().bounds();
      }
      devtools_bounds_.set_x(display.x() +
                             (display.width() - devtools_bounds_.width()) / 2);
      devtools_bounds_.set_y(
          display.y() + (display.height() - devtools_bounds_.height()) / 2);
    }
  }
  g_web_contents_instances_.push_back(this);
}
InspectableWebContents::~InspectableWebContents() {