Woops, how did that happen ;)

atom/browser/api/atom_api_app.cc

@@ -533,6 +533,8 @@ App::~App() {
   content::BrowserChildProcessObserver::Remove(this);
 }
 
+App* App::self_ = nullptr;
+
 App* App::Get() {
   return App::self_;
 }

atom/browser/api/atom_api_app.h

@@ -101,7 +101,7 @@ class App : public AtomBrowserClient::Delegate,
  protected:
   explicit App(v8::Isolate* isolate);
   ~App() override;
-  static App* self_ = nullptr;
+  static App* self_;
 
   // BrowserObserver:
   void OnBeforeQuit(bool* prevent_default) override;