BUG_FIX: add condition check for app->window, make sure it's not null
before call EGLRenderer Init();
OTHER: remove redundant LOGD();
BUG_FIX:
- make glClearColor be red, but not dark which is hard to identify;
- add condition check in Init(), make sure app->window is not null before
  run the EGL init. If app->window is null, it will bring crash when call
  ANativeWindow_XXX;
- make the assert be more precise
- add m_bRendering to be true at the end of Init(), which will make
  RenderFrame() be executable and glClear() will be run
OTHER:
- remove redundant LOGD
OTHER:
- remove redundant LOGD