title: Swagger Codegen - Unexpected missing property for name response
body: <p>I am trying to generate node.js-server stub using codegen. I have downloaded the <code>swagger-codegen-cli-2.3.1.jar</code> file and am trying to generate the code using cli command. 
  However, it is failing with the following error message:</p>
  
  <pre><code>[main] ERROR io.swagger.codegen.DefaultCodegen - unexpected missing property for name response
  [main] WARN io.swagger.codegen.DefaultCodegen - skipping invalid array property {
    "baseName" : "response",
    "getter" : "getResponse",
     ....
    "isReadOnly" : false,
    "vendorExtensions" : { },
    "hasValidation" : false,
    "isXmlAttribute" : false,
    "isXmlWrapped" : false
  }
  [main] ERROR io.swagger.codegen.DefaultCodegen - unexpected missing property for name response
  Exception in thread "main" java.lang.RuntimeException: Could not process operation:
    Tag: Tag {
          name: messages
          description: Messages for blue instance
          externalDocs: null
          extensions:{}}
    Operation: listMessages
    Resource: get /instances/{instanceId}/messages
    Definitions: {message-common=io.swagger.models.ModelImpl@e68ed4e0, Error Response=io.swagger.models.ModelImpl@7bcf5e6c}
    Exception: null
          at io.swagger.codegen.DefaultGenerator.processOperation(DefaultGenerator.java:932)
          at io.swagger.codegen.DefaultGenerator.processPaths(DefaultGenerator.java:808)
          at io.swagger.codegen.DefaultGenerator.generateApis(DefaultGenerator.java:431)
          at io.swagger.codegen.DefaultGenerator.generate(DefaultGenerator.java:746)
          at io.swagger.codegen.cmd.Generate.run(Generate.java:285)
          at io.swagger.codegen.SwaggerCodegen.main(SwaggerCodegen.java:35)
  Caused by: java.lang.NullPointerException
          ... 5 more
  </code></pre>
  
  <p>Here is an excerpt from my swagger definitions file. 
  I did adding/removing <code>x-swagger-router-controller</code> attribute, but that did not help either.</p>
  
  <pre><code>swagger: '2.0'
  info:
    title: Messages API
    version: '1.0'
    description: |-
      Call used to get messages
  host: 'localhost:8080'
  paths:
    '/instances/{instanceId}/messages':
      get:
        summary: Get all messages
        operationId: listMessages
        responses:
          '200':
            description: 'Success Response'
            schema:
              type: array
              items:
                title: Message Output
                description: The properties that are included
                allOf:
                  - type: object
                    properties:
                      id:
                        type: string
                  - title: Message Common
                    description: The properties that are shared
                    type: object
                    properties:
                      message:
                        type: string
                        description: Operation the system must do
                      details:
                        type: string
                        description: 'Textual data'
                    required:
                      - message
                      - details
          '401':
            description: Unauthorized requests
            schema:
              type: object
              title:  Error Response
              description: Standard  error message.
              properties:
                errors:
                  type: array
                  items:
                    type: object
                    properties:
                      code:
                        type: string
                        description: Human readable category
                      message:
                        type: string
                        description: Detailed error message
                    required:
                      - code
                      - message
              required:
                - errors
          '500':
            description: Response for other issues
            schema:
              type: object
              title:  Error Response
              description: Standard  error message.
              properties:
                errors:
                  type: array
                  items:
                    type: object
                    properties:
                      code:
                        type: string
                        description: Human readable category
                      message:
                        type: string
                        description: Detailed error message
                    required:
                      - code
                      - message
              required:
                - errors
        description: 'Call used to get messages, notices, and/or instructions from E&amp;E system for the product to take. '
        parameters:
          - name: Digest
            in: header
            type: string
            description: The digest for the body being passed
        tags:
          - messages
      parameters:
        - name: instanceId
          in: path
          type: string
          required: true
          description: The specific instance for which the message is relevant
  basePath: /v1
  schemes:
    - http
  consumes:
    - application/json
  produces:
    - application/json
  tags:
    - name: messages
      description: Messages for instance
  </code></pre>
  
  <p>Please help. Not sure what I am missing here.</p>