there can be no saver available (blackness)

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@13989 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kits/screensaver/ScreenSaverThread.cpp

@@ -36,6 +36,7 @@ ScreenSaverThread::ScreenSaverThread(BWindow *wnd, BView *vw, ScreenSaverPrefs *
 void 
 ScreenSaverThread::Quit() 
 {
+	if (fSaver)
 		fSaver->StopSaver();
 	if (fWin)
 		fWin->Hide();
@@ -48,6 +49,7 @@ ScreenSaverThread::Thread()
 	fWin->Lock();
 	fView->SetViewColor(0,0,0);
 	fView->SetLowColor(0,0,0);
+	if (fSaver)
 		fSaver->StartSaver(fView,false);
 	fWin->Unlock();
 	while (1) {