Use fadescreen constants

src/item_use.c

@@ -601,7 +601,7 @@ void ItemUseOutOfBattle_PokeblockCase(u8 taskId)
     else
     {
         gFieldCallback = sub_80AF6D4;
-        FadeScreen(1, 0);
+        FadeScreen(FADE_TO_BLACK, 0);
         gTasks[taskId].func = sub_80FDC00;
     }
 }