don't init general background graphics in the first LoadNextSong call

stepmania/src/ScreenGameplay.cpp

@@ -654,6 +654,8 @@ void ScreenGameplay::Init()
 		}
 	}
 	
+	m_SongBackground.Init();
+
 	if( !GAMESTATE->m_bDemonstrationOrJukebox )	// only load if we're going to use it
 	{
 		m_soundAssistTick.Load(	THEME->GetPathS(m_sName,"assist tick"), true );