fix "save prefs when exiting system menu"; when DelayedScreenLoad,

bWasOnSystemMenu was always false, because the screen was already
deleted

stepmania/src/ScreenManager.cpp

@@ -361,6 +361,8 @@ void ScreenManager::SetNewScreen( const CString &sScreenName )
 
 void ScreenManager::LoadDelayedScreen()
 {
+	const bool bWasOnSystemMenu = !m_ScreenStack.empty() && m_ScreenStack.back()->GetScreenType() == system_menu;
+
 	/*
 	 * We have a screen to display.  Delete the current screens and load it.
 	 * If DelayedScreenLoad is true, clear the old screen first; this lowers
@@ -377,8 +379,6 @@ retry:
 	CString sScreenName = m_sDelayedScreen;
 	m_sDelayedScreen = "";
 
-	Screen* pOldTopScreen = m_ScreenStack.empty() ? NULL : m_ScreenStack.back();
-
 
 	//
 	// Search prepped screens to see if we already have this screen available.
@@ -428,7 +428,6 @@ retry:
 		m_sLastLoadedBackgroundPath = sNewBGA;
 	}
 
-	bool bWasOnSystemMenu = pOldTopScreen  &&  pOldTopScreen->GetScreenType() == system_menu;
 	bool bIsOnSystemMenu = pNewScreen->GetScreenType() == system_menu;
 	
 	// If we're exiting a system menu, persist settings in case we don't exit normally