`./xdp_ddos01_blacklist_cmdline --list` reports segmentation fault

```
./xdp_ddos01_blacklist_cmdline --list
{
 "172.20.0.1" : 0,
 "198.18.50.3" : 0,
 "80" : {
	"UDP" : 0
 }
}
Segmentation fault (core dumped)
```