Segmentation fault while executing `conf get` in JSON format

[fluca1978]

pgagroal version 4d14643, when doing conf get in JSON format there is a segfault:

% pgagroal-cli conf -F json set log_level debug
{
        "command":      {
                "name": "conf set",
                "status":       "OK",
                "error":        0,
                "exit-status":  0,
                "output":       {
                        "key":  "log_level",
                        "value":        "debug",
                        "expected":     "debug"
                }
        },
        "application":  {
                "name": "pgagroal-cli",
                "major":        1,
                "minor":        6,
                "patch":        0,
                "version":      "1.6.0"
        }
}

`zsh:` segmentation fault  pgagroal-cli conf -F json set log_level debug

The other JSON commands seems to be find.