Fix GUI crashes when exiting STK by clicking the X button in the window titlebar

src/graphics/irr_driver.cpp

@@ -1931,8 +1931,9 @@ void IrrDriver::update(float dt)
     // =================================
     if (!m_device->run())
     {
-        GUIEngine::cleanUp();
+        // Don't bother cleaning up GUI, has no use and may result in crashes
-        GUIEngine::deallocate();
+        //GUIEngine::cleanUp();
+        //GUIEngine::deallocate();
         main_loop->abort();
         return;
     }