Trying to get property of non-object in Laravel 5

I'm getting the ErrorException: Trying to get property of non-object

I'm trying to display all the relationship that is link using this function. The relationship is ->

-Card can have many notes, Notes only have one card. -Each notes contain only one user, User contain only one card. My code is:

Model

1. Note

   class Note extends Model { protected $fillable = ['body'];

   public function cards()
   {
       return $this->belongsTo(Card::class);
   }
   
   public function users()
   {
       return $this->belongsTo(User::class,'id');
   }
   
   

   }

2. User

   class User extends Authenticatable { use Notifiable;

   public function note()
   {
       return $this->belongsTo(Note::class);
   }
   
   protected $fillable = [
       'name', 'email', 'password',
   ];
   
   protected $hidden = [
       'password', 'remember_token',
   ];
   
   

   }

3. Card

   class Card extends Model { public function notes() { return $this->hasMany(Note::class);//relationship }

   public function addNote(Note $note)
   {
       return $this->notes()->save($note);
   }
   
   

   }

Controller

1. cardsController

   class cardsController extends Controller { public function index() { $cards = Card::all(); return view('cards.index',compact('cards')); }

   public function show(Card $card)
   {
       $card->load('notes.user'); **The Error is here.**
       $return $card;
       return view('cards.show',compact('card'));
   
   
   }
   
   

   }

2. notesController

   class notesController extends Controller {

   public function store(Request $request, Card $card)
   {
       $card->addNote(
               new Note($request->all())
           ); 
   
       return back();
   }
   
   public function edit(Note $note)
   {
       return view('notes.edit',compact('note'));
   }
   
   public function update(Request $request, Note $note)
   {
       $note -> update($request -> all());
   
       return back();
   }
   
   

   }

DB

1. notes table

$card->load('notes.user'); -when i just put (notes) in the cardControllers function, it will appear all data that link from card and notes table. -but when i try to add (notes.user) it said that trying to get non property obejct. Am i missing something?

via Chebli Mohamed