app: errors when attempting to use team plugin on latest code sha - 511b54dafc7a020bd6fb66bd838d0741f1391c45

The following error is given when attempting to set teams as follows

  - name: team1
    permission: admin
  - name: team2
    permission: push

   TypeError: Cannot read property 'then' of undefined
       at Teams.add (/app/node_modules/probot-settings/lib/plugins/teams.js:25:26)
       at /app/node_modules/probot-settings/lib/plugins/diffable.js:40:31
 19:31:01.734Z ERROR event: Cannot read property 'then' of undefined (id=c92449a6-04b9-11ea-9112-c1b7a775726e)
       at Array.forEach (<anonymous>)
       at /app/node_modules/probot-settings/lib/plugins/diffable.js:34:22
       at async Promise.all (index 2)
   --
   event: {
   TypeError: Cannot read property 'then' of undefined
       at Teams.add (/app/node_modules/probot-settings/lib/plugins/teams.js:25:26)
       at /app/node_modules/probot-settings/lib/plugins/diffable.js:40:31
     "event": "push",
     "id": "c92449a6-04b9-11ea-9112-c1b7a775726e",
       at Array.forEach (<anonymous>)
       at /app/node_modules/probot-settings/lib/plugins/diffable.js:34:22
     "installation": 3511132,
     "repository": "myorg/test"
   }
 19:31:01.735Z ERROR probot: Cannot read property 'then' of undefined
       at async Promise.all (index 2)
   --
   event: {
     "event": "push",
     "id": "c92449a6-04b9-11ea-9112-c1b7a775726e",
   TypeError: Cannot read property 'then' of undefined
       at Teams.add (/app/node_modules/probot-settings/lib/plugins/teams.js:25:26)
     "installation": 3511132,
     "repository": "myorg/test"
   }
 19:31:01.735Z ERROR probot: Cannot read property 'then' of undefined
   TypeError: Cannot read property 'then' of undefined
       at Teams.add (/app/node_modules/probot-settings/lib/plugins/teams.js:25:26)
       at /app/node_modules/probot-settings/lib/plugins/diffable.js:40:31
       at /app/node_modules/probot-settings/lib/plugins/diffable.js:40:31
       at Array.forEach (<anonymous>)
       at Array.forEach (<anonymous>)
       at /app/node_modules/probot-settings/lib/plugins/diffable.js:34:22
       at /app/node_modules/probot-settings/lib/plugins/diffable.js:34:22
       at async Promise.all (index 2)
 19:31:01.735Z  INFO http: POST / 500 - 2983.62 ms (id=c92449a6-04b9-11ea-9112-c1b7a775726e)
       at async Promise.all (index 2)
 19:31:01.735Z  INFO http: POST / 500 - 2983.62 ms (id=c92449a6-04b9-11ea-9112-c1b7a775726e)
 19:31:02.314Z ERROR probot: Resource not accessible by integration
   HttpError: Resource not accessible by integration
       at /app/node_modules/@octokit/request/dist-node/index.js:66:23
       at processTicksAndRejections (internal/process/task_queues.js:93:5)
       at async Job.doExecute (/app/node_modules/bottleneck/light.js:405:18)
 19:31:02.314Z ERROR probot: Resource not accessible by integration
   HttpError: Resource not accessible by integration
       at /app/node_modules/@octokit/request/dist-node/index.js:66:23
       at processTicksAndRejections (internal/process/task_queues.js:93:5)
       at async Job.doExecute (/app/node_modules/bottleneck/light.js:405:18)```