#vulnerable code 
                             @Override
	public void processEvent(SystemEvent event) throws AbortProcessingException {
		if (event instanceof PreDestroyViewMapEvent) {
			BeanManager.INSTANCE.getReference(ViewScopeManager.class).preDestroyView();
		}
	} 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             @Override
	public void processEvent(SystemEvent event) throws AbortProcessingException {
		if (event instanceof PreDestroyViewMapEvent) {
			processPreDestroyView();
		}
		else if (event instanceof PostRestoreStateEvent && "unload".equals(getRequestParameter("omnifaces.event"))) {
			processPreDestroyView();
			responseComplete();
		}
	}