问Laravel 8:试图获取非对象的属性“id”

EN

Route::get('folders-materials/{url}', [App\Http\Controllers\TeamsController::class, 'folderMaterialAdminUrl']);

public function folderMaterialAdminUrl(Request $request, $url=null) {
        $teams = Team::where('url', $url)->first();

        $folders = Folder::where('url', $url)->first();
        $subfolders = Subfolder::where('folder_id', $folders->id)->where('user_team',$teams->id)->orderBy('id', 'asc')->get();
        $files = File::where('folder_upload', $folders->id)->orderBy('created_at', 'DESC')->get();

        return view('adminsubfolderurl')->with(compact('teams','folders','subfolders','files'));
    }

@foreach ($subfolders as $subfolder_admin)
   <div class="col-xl-3 col-lg-4 col-md-4 col-sm-6 pt-5">
      <a href="{{ url('subfolders/'.$subfolder_admin->url) }}" class="folder-link">
          <i class="fas fa-folder d-flex justify-content-center m-auto"></i>
          <div class="user-inf pt-4 text-center">
              <h3>{{ $subfolder_admin->name }}</h3>
          </div>
      </a>
  </div>
@endforeach

@foreach ($files as $file_admin)
  <div class="col-xl-3 col-lg-4 col-md-4 col-sm-6 pt-5 file-col">
      <a href="/{{ $file_admin->file }}" target="_blank" class="file-link">
          <i class="far fa-image d-flex justify-content-center m-auto"></i>
          <div class="user-inf pt-4 text-center">
              <h3>{{ $file_admin->name }}</h3>
              <p>{{ $file_admin->created_at }}</p>
          </div>
      </a>
  </div>
@endforeach