#fixed code
                                @Path("{username}/session-stats")
    @GET
    @NoCache
    @Produces(MediaType.APPLICATION_JSON)
    public Map<String, UserStats> getSessionStats(final @PathParam("username") String username) {
        logger.info("session-stats");
        auth.requireView();
        UserModel user = realm.getUser(username);
        if (user == null) {
            throw new NotFoundException("User not found");
        }
        Map<String, UserStats> stats = new HashMap<String, UserStats>();
        for (ApplicationModel applicationModel : realm.getApplications()) {
            if (applicationModel.getManagementUrl() == null) continue;
            UserStats appStats = new ResourceAdminManager().getUserStats(realm, applicationModel, user);
            if (appStats == null) continue;
            if (appStats.isLoggedIn()) stats.put(applicationModel.getName(), appStats);
        }
        return stats;
    }
#vulnerable code 
                                @Path("{username}/session-stats")
    @GET
    @NoCache
    @Produces(MediaType.APPLICATION_JSON)
    public Map<String, UserStats> getSessionStats(final @PathParam("username") String username) {
        logger.info("session-stats");
        auth.requireView();
        UserModel user = realm.getUser(username);
        if (user == null) {
            throw new NotFoundException("User not found");
        }
        Map<String, UserStats> stats = new HashMap<String, UserStats>();
        for (ApplicationModel applicationModel : realm.getApplications()) {
            if (applicationModel.getManagementUrl() == null) continue;
            UserStats appStats = new ResourceAdminManager().getUserStats(realm, applicationModel, user);
            if (appStats.isLoggedIn()) stats.put(applicationModel.getName(), appStats);
        }
        return stats;
    } 
                            #location 16 
                            #vulnerability type NULL_DEREFERENCE