Problem statement

When defining a response model

      modelName:
        type: array
        items:
          type: string
        $ref: '#/definitions/someDefinition'

the swagger is considered valid but the generator crashes

Swagger specification

described above

Steps to reproduce

1. Create the swagger.yml with the model above
2. Try create the models with swagger generate model --spec=swagger.yml -m=./models
3. Crash

Environment

swagger version: v0.26.0
go version: v1.15.6
OS: Manjaro