#vulnerable code 
                                @EventHandler
    public void blockFormEvent(BlockFormEvent event) {
        if (event.getBlock().getType() == Material.SNOW) {
            double temp = ClimateEngine.getInstance().getClimateEngine(event.getBlock().getWorld().getName()).getTemperature();

            if (event.getBlock().getY() < MapUtil.searchTreeMap(heightMap, temp)) {
                event.setCancelled(true);
            }
        }
    } 
                            #location 6 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @EventHandler
    public void blockFormEvent(BlockFormEvent event) {
        if (event.getNewState().getType() == Material.ICE) {
            double temp = ClimateEngine.getInstance().getClimateEngine(event.getBlock().getWorld().getName()).getTemperature();

            if (event.getBlock().getY() < heightMap.getValue(temp)) {
                event.setCancelled(true);
            }
        }
    }