Validation of schema using $ref always returns true

[nine]

Observed behavior

The validation of following Json schema using the $ref keyword always returns true.

{
    "$schema": "http://json-schema.org/draft-07/schema#",
    "title": "Schedule",
    "type": "object",
    "properties": {
        "reply": {
            "description": "Send reply",
            "type": "boolean"
        },
        "schedule": {
            "description": "Array with schedule entries",
            "type": "array",
            "items": { "$ref": "#/definitions/schedule_entry" }
        }
    },
    "definitions": {
        "schedule_entry": {
            "type": "object",
            "required": [
                "id",
                "startdate",
                "cmd",
                "settings"
            ],
            "properties": {
                "id": {
                    "type": "string"
                },
                "startdate": {
                    "type": "number",
                    "minimum": 0
                },
                "cmd": {
                    "type": "string"
                },
                "settings": {
                    "type": "object"
                }
            }
        }
    }
}

Tested with

1. valid object:

   {
   "reply": false, 
   "schedule": [
       {
           "id": "abc",
           "startdate": 1,
           "cmd": "foo",
           "settings": {}
       }
   ]
   }

2. invalid object

   { "foo": "bar" }

Expected behavior

The validation of the second Json instance should return false.

Steps to reproduce A unit test for the bug is available in #219.

[nine]

Discovered missing "required" array that caused wrong expectations on validation behavior. json-schema-validator works as expected!