Destroy history after scene.

src/context.cpp

@@ -21,15 +21,15 @@ Context::~Context() {
 	delete patch;
 	patch = NULL;
 
-	delete history;
-	history = NULL;
-
 	delete scene;
 	scene = NULL;
 
 	delete event;
 	event = NULL;
 
+	delete history;
+	history = NULL;
+
 	delete engine;
 	engine = NULL;
 }