[BUG][csharp-nancyfx] An invalid c# Modules file is created under certain conditions

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?

Description

Sometimes (I'm not sure what's the trigger), the c# nancyfx code generator emits an empty (and invalid) "using ;") line in a Modules file.

openapi-generator version

master

OpenAPI declaration file content or url

swagger: "2.0"
info:
  version: "0.0.1"
  title: "bug"
host: "localhost:8080"
basePath: "/v1alpha1"
schemes:
- "http"
paths:
  /test:
    post:
      parameters:
      - in: "body"
        name: "body"
        schema:
          type: "object"
          properties:
            name:
              type: "string"
      responses:
        "204":
          description: "successful operation"

Generation Details

standard csharp-nancyfx generation.

Steps to reproduce

generate the above spec file and look in the file: src/Org.OpenAPITools/Modules/DefaultModule.cs

Related issues/PRs

Suggest a fix

Generate the provided Swagger 2.0 specification with the csharp-nancyfx generator, then inspect src/Org.OpenAPITools/Modules/DefaultModule.cs. Trace the template or generator path responsible for the Modules file and identify why an empty using directive is emitted. Done means the generated file contains no invalid "using ;" line for this reproduction.