Error creating subscription in playground

[jmandel]

From the playground, trying to create a subscription with two filters:

Request for Subscription (https://server.subscriptions.argo.run/Subscription/) failed: TypeError: t.push is not a function

There's a request being made as POST https://server.subscriptions.argo.run/Subscription/ , returning:

{
  "resourceType": "Subscription",
  "channel": {
    "endpoint": "https://client.subscriptions.argo.run/Endpoints/4af133c8-8693-4c57-ac1a-420c8f23017d",
    "header": [],
    "heartbeatPeriod": 60,
    "payload": {
      "content": "id-only",
      "contentType": "application/fhir+json"
    },
    "type": {
      "coding": [
        {
          "code": "rest-hook",
          "display": "Rest Hook",
          "system": "http://terminology.hl7.org/CodeSystem/subscription-channel-type",
          "userSelected": false
        }
      ],
      "text": "REST Hook"
    }
  },
  "end": "2019-09-13T01:01:22.030Z",
  "eventCount": 0,
  "filterBy": [
    {
      "matchType": "=",
      "name": "patient",
      "value": "Patient/"
    }
  ],
  "reason": "Client Testing",
  "status": "requested",
  "topic": {
    "reference": "Topic/1"
  },
  "id": "e30239b9-8486-4a04-b911-d755d80fd6dd"
}

Note: there shouldn't be a trailing slash at the end of the /Subscription/ URL, but this probably isn't related.