导入swagger文件失败，格式经过swagger.editor验证

[hua-js]

Bug 描述
Uncaught (in promise) TypeError: Cannot convert undefined or null to object
at Function.keys ()
at importDataTypes (/src/lib/NEI_import/dist/NEISwagger.js:13399)
at /src/lib/NEI_import/dist/NEISwagger.js:13436

预期期望
如果是文件格式错误，希望能有个demo参照；
如果格式没有错误，我应该如何使用导入swagger这个功能

导入文件
swagger: '2.0'
info:
version: 1.0.0
title: Simple Artist API
description: A simple API to understand the Swagger Specification in greater detail
schemes:

• https
  host: example.io
  basePath: /v1
  securityDefinitions:
  UserSecurity:
  type: basic
  security:

  • UserSecurity: []
    paths:
    /artists:
    get:
    description: Returns a list of artists
    parameters:
    - name: limit
    in: query
    type: integer
    description: Limits the number of items on a page
    - name: offset
    in: query
    type: integer
    description: Specifies the page number of the artists to be displayed

    responses:
    200:
    description: Successfully returned a list of artists
    schema:
    type: array
    items:
    type: object
    required:
    - username
    properties:
    artist_name:
    type: string
    artist_genre:
    type: string
    albums_recorded:
    type: integer
    username:
    type: string

    400:
      description: Invalid request 
      schema:
        type: object
        properties:   
          message:
            type: string
    

    post:
    description: Lets a user post a new artist
    parameters:
    - name: artist
    in: body
    description: creates a new artist in our database
    schema:
    type: object
    required:
    - username
    properties:
    artist_name:
    type: string
    artist_genre:
    type: string
    albums_recorded:
    type: integer
    username:
    type: string

    responses:
    200:
    description: Successfully created a new artist

    400:
      description: Invalid request 
      schema:
        type: object
        properties:   
          message:
            type: string
    

  ----- Added lines ----------------------------------------

  /artists/{username}:
  get:
  description: Obtain information about an artist from his or her unique username
  parameters:
  - name: username
  in: path
  type: string
  required: true

  responses:
    200:
      description: Successfully returned an artist
      schema:
        type: object
        properties:
          artist_name:
            type: string
          artist_genre:
            type: string
          albums_recorded:
            type: integer
            
    400:
      description: Invalid request
      schema:
        type: object 
        properties:           
          message:
            type: string
  

  ---- /Added lines ----------------------------------------

[xuchaoying]

这是由于没有对数据模型判空导致的bug，我们稍后修复