Playground: code completion bug

[mandel59]

Steps to Reproduce:

{
  "@context": "http://schema.org/",
  "@type": "Person",
  "email": "mailto:jane"
}

1. Copy the above json-ld to the playground, or use this permalink.
2. Move the cursor right after mailto:jane.
3. Type @, then you will see a growing @ sequence as the image below.