Clear target if loading screen is unavailable

This fixes visible precache that you should not see

Author: Xottab-DUTY

src/xrEngine/x_ray.cpp

@@ -519,4 +519,6 @@ void CApplication::load_draw_internal()
 {
     if (loadingScreen)
         loadingScreen->Update(load_stage, max_load_stage);
+    else
+        GEnv.Render->ClearTarget();
 }