Segmentation fault with char-to in while

rule
```
version=2

rule=:a %
        {"name":"numbers", "type":"repeat",
            "parser":
                     {"type":"number", "name":"n"},
            "while":
                     {"type":"char-to", "name":"host", "extradata":":"}
         }% b
```

payload
```
a 1 : 2 b
```

liblognorm version: 2.0.4