Re-set demo controller on sector transition

Fixes bug 115 http://supertux.lethargik.org/bugs/view.php?id=115

src/supertux/game_session.cpp

@@ -361,6 +361,7 @@ GameSession::update(float elapsed_time)
     sector->play_music(LEVEL_MUSIC);
     currentsector = sector;
     currentsector->play_looping_sounds();
+    reset_demo_controller();
     //Keep persistent across sectors
     if(edit_mode)
       currentsector->get_players()[0]->set_edit_mode(edit_mode);

src/supertux/game_session_recorder.cpp

@@ -110,9 +110,7 @@ GameSessionRecorder::play_demo(const std::string& filename)
     throw std::runtime_error(msg.str());
   }
 
-  Player& tux = *GameSession::current()->get_current_sector()->player;
-  demo_controller = new CodeController();
-  tux.set_controller(demo_controller);
+  reset_demo_controller();
 
   // skip over random seed, if it exists in the file
   char buf[30];                            // ascii decimal seed
@@ -123,6 +121,18 @@ GameSessionRecorder::play_demo(const std::string& filename)
     playback_demo_stream->seekg(0);     // old style w/o seed, restart at beg
 }
 
+void
+GameSessionRecorder::reset_demo_controller()
+{
+  if(demo_controller == NULL)
+  {
+    demo_controller = new CodeController();
+  }
+  auto game_session = GameSession::current();
+  auto player = game_session->get_current_sector()->player;
+  player->set_controller(demo_controller);
+}
+
 void
 GameSessionRecorder::process_events()
 {

src/supertux/game_session_recorder.hpp

@@ -33,6 +33,12 @@ class GameSessionRecorder
   void play_demo(const std::string& filename);
   void process_events();
 
+  /**
+   * Re-sets the demo controller in case the sector
+   * (and thus the Player instance) changes. 
+   */
+  void reset_demo_controller();
+
 private:
   void capture_demo_step();