Unable to generate libdoc

Hello,

Since version 4.1.1, the documentation cannot be generated anymore:

```shell
$ libdoc Remote::http://127.0.0.1:8270/ClientLib list
> Calling dynamic method 'get_keyword_documentation' failed: KeyError: '__intro__'
```

Note that if I revert to 4.1.0 it works, but I am having exceptions thrown on server side (but at least my client manages to get the doc)