Nil pointer dereference exception while validate an swagger without path

[lixingwang]

I want to use go-swagger validation feature so I defined an very simple swagger without paths, see the swagger file:

"swagger" : "2.0",
  "info" : {
    "version" : "1.0",
    "title" : "Hello World",
    "description" : "Simple Hello World API, with Get operation to one resource path, no request parameters defined"
  },
  "host" : "api.tibco.com",
  "basePath" : "/v1",
  "schemes" : [ "http" ]
}

Then it throw nil point exception, we hope it might return error with "Invalid swagger content, please provide paths....."

Hope this can be fixs.

Thanks,
Tracy