fixed alpha transition

src/flow/Transition.cpp

@@ -139,7 +139,7 @@ namespace oxygine
 #if OXYGINE_RENDERER>3
             //target->getHolder()->setAlpha(back ? 255 : 0);
             spTween tween = target->getHolder()->addTween(
-                                TweenAlphaFade(!back, PostProcessOptions().fullscreen()), duration, 1, false, 0);
+                                TweenAlphaFade(!back, PostProcessOptions().fullscreen().clear(Color(0, 0, 0, 255))), duration, 1, false, 0);
 #elif OXYGINE_RENDERER>2
             //target->getHolder()->setAlpha(back ? 255 : 0);
             spTween tween = target->getHolder()->addTween(