Ember get filtered data from the store/mirage

I am trying to build an app for smarthome devices with ember. I already have installed mirage and declare an array which is called data. It holds arrays like households, users and devices. Now I am stuck with get filtered data from the store and i am really confused by the behaviour of the store. For this reason I already read some equal topics like this Filtering store data in ember but this doesn´t work in my case.

Actually this is my router.js

Router.map(function() {
  this.route('about');
  this.route('users', function() {
  });
  this.route('households', function() {
    this.route('index', { path: '/:user_id' })
    this.route('rooms',{ path: '/:household_id' });
    this.route('devices');
  });
});

If I am going to households.index I want to see all households which have the user-id in his member-array. The following code snipped shows an example of my data-structure.

  "users": [
      {
          "id":101,
          "forename":"Peter",
          "surname":"Peterson",
          "memberIn":[
              501
          ]
      },
      {
          "id":102,
          "forename":"Anna",
          "surname":"Peterson",
          "memberIn":[
              501
          ]
      }
]

  "households":[
      {
          "id":501,
          "name":"Zuhause",
          "admin":131000,
          "member":[
              101,
              102
          ]
}

I am calling the route household.index like this and my route in household.index looks like this

model(params) {
    //holt alle Haushalte und gibt dann nur die Haushalte weiter, die auch den aktuellen Benutzer als Member haben.
   return this.get('store').findAll('household').then(results => results.filter((site) => {
       return site.get('member').filter(x => x == params.user_id).length > 0;
   }));
  } 

And my config.js part at mirage like this:

  this.get('/households', function(db, request) {
    return { households: data.households };   
});

This works fine! But in my opinion the server is responsible for giving me the data I am requesting for. So all I want is that I send a specific request and just get the households that I need.

My attempt: index.js:

export default Route.extend({
    model(params) {
        return this.get('store').find('household', params.user_id);
      }
});

config js part:

  this.get('/households/:id', function(db, request) {
      console.log('household get');
      console.log(data.households.filter(x => x.member.filter(x => x == request.params.id).length > 0));
    return  { households: data.households.filter(x => x.member.filter(x => x == request.params.id).length > 0) };   
});

Debug Error:

Error while processing route: households.index payload.data is null

I cant understand why this error occurs. The log gives me the array i want to return.