It seems this package doesn't currently support creating an issue with no labels. It works fine when there's at least one label, otherwise the Client.CreateIssue call errors out with:

graphql error: Variable $Labels of type [ID!]! was provided invalid value

I think the problem is exactly one ! character on this line:

The variable Label is a required list of required IDs (two instances of "required"). It can be relaxed to be an optional list of required IDs (one instance of "required"), which is what the createIssue mutation GitHub GraphQL schema expects for its labelIds field: