Invalid AST Node: false

[shmax]

@vladar
While working on optimizations, I updated my local code to master, and am now seeing this error whenever I use an include directive:

{
  "error": {
    "message": "Invalid AST Node: false"
  }
}

It's easy to reproduce. You can run the 02-blog sample, and run this query:

{
  viewer {
    id @include (if: true)
  }
}

The culprit seems to be this commit: cab1599

Somehow, the false value returned here becomes the value of node and trips an exception here.

If I remove the boolean returns then everything starts working again, but then some of the tests fail. I thought I'd throw an issue up here to see if you have any thoughts. Thanks much.