UI: Prevent race condition during emulator startup.

src/xenia/app/emulator_window.cc

@@ -266,6 +266,8 @@ bool EmulatorWindow::Initialize() {
 
   window_->Resize(1280, 720);
 
+  window_->DisableMainMenu();
+
   return true;
 }
 

src/xenia/app/xenia_main.cc

@@ -178,6 +178,9 @@ int xenia_main(const std::vector<std::wstring>& args) {
     evt->Set();
   });
 
+  // Enable the main menu now that the emulator is properly loaded
+  emulator_window->window()->EnableMainMenu();
+
   // Grab path from the flag or unnamed argument.
   std::wstring path;
   if (!FLAGS_target.empty() || args.size() >= 2) {