Laravel 8: Trying to get property 'id' of non-object - laravel-8

Question

I am trying to show subfolders and files (eg docx, pdf, png) in οther parent folders but I am getting this error "Trying to get property 'id' of non-object".
This is my route:
Route::get('folders-materials/{url}', [App\Http\Controllers\TeamsController::class, 'folderMaterialAdminUrl']);
This is my controller:
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', $folders->id)->orderBy('created_at', 'DESC')->get();
return view('adminsubfolderurl')->with(compact('teams','folders','subfolders','files'));
}
and this is my blade:
#foreach ($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
Can anyone help please?

Answer 1

When you bind data through url and can be optional you have to use the '?' symbol, otherwise $url = null always is null
Route::get('folders-materials/{url?}', [App\Http\Controllers\TeamsController::class, 'folderMaterialAdminUrl']);
https://laravel.com/docs/8.x/routing#parameters-optional-parameters
Like I see, you don't need to assign null value to $url binded parameter if you use it for retrieve from db. Just
public function folderMaterialAdminUrl(Request $request, $url) {
$teams = Team::where('url', $url)->first();