Broken images when using json view formatter

Question

https://github.com/pnp/sp-dev-list-formatting/blob/master/view-samples/contact-card-format/contact-card-format.json

I am using a code from above link, I have changed all $Picture to make list value, weird thing is when I remove the JSON code the image shows:

attributes": {
     "src": "=if([$Picture] == '', @currentWeb + '/_layouts/15/userphoto.aspx?size=M', [$Picture])",
     "title": "=if([$Picture] == '', 'No picture available', [$Picture.desc])"
}