no error on wildcard expected but undefined ?!

[andreineculau]

it seems strange, and potentially a bug that

{
  "foo": "{{_}}",
  "{{_}}": "{{unexpected}}"
}

will not fail if the payload is actually the empty object {}

[andreineculau]

seems like a breaking change was not identified in the 1.3.0 release
c661b85 allow {{_}} to match nothing

this means that a new keyword {{expected}} needs to be added if one wants to require a value