fix: eliminates intermittent flicker with UI; NO_UI shouldn't be allowed for :setup events

addons/escoria-core/game/main.gd

@@ -222,6 +222,8 @@ func check_game_scene_methods():
 
 	assert(current_scene.game.has_method("hide_ui"))
 	assert(current_scene.game.has_method("show_ui"))
+	assert(current_scene.game.has_method("escoria_hide_ui"))
+	assert(current_scene.game.has_method("escoria_show_ui"))
 	assert(current_scene.game.has_method("_on_event_done"))