Fixed Device manager: restore gmainloop

The gmainloop is used by gst to detect devices. Fixed bugs on detection of invalid devices.

RenderingManager.cpp

@@ -352,10 +352,8 @@ void Rendering::draw()
     // Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
     glfwPollEvents();
 
-#ifndef USE_GST_APPSINK_CALLBACKS
     // no g_main_loop_run(loop) : update global GMainContext
     g_main_context_iteration(NULL, FALSE);
-#endif
 
 }