laravelError

//in web.php:
Route::post('/profile/edit/save', 'AccountUserController@saveProfile')->name('save_profile');

// html code
<form class="profile-data" enctype="multipart/form-data" method="POST" action="{{ route('save_profile') }}">
             {{ csrf_field() }}
             <input type="hidden" name="id_user" value="{{ $user->id}}">
             <div class="row r-avatar">
              <div class="col-md-4" style="border:0px solid">
                 <img src="{{ URL::asset('frontend/img/avatars/')}}/{{ $user->user_avatar}}" alt="Avatar" style="width:100px;height:100px;max-width: none;" class="img-thumbnail img-circle">
              </div>
              <div class="col-md-8 profile-txt" style="border:0px solid">
                <input type="file" name="user_avatar">
              </div>
            </div><br>
            <div class="row r-username">
              <div class="col-md-4" style="border:0px solid">
                 Username:
              </div>
              <div class="col-md-8 profile-txt" style="border:0px solid">
               {{ $user->username}}
              </div>
            </div><br>
            <div class="row r-email">
              <div class="col-md-4" style="border:0px solid">
                 Email:
              </div>
              <div class="col-md-8 profile-txt" style="border:0px solid">
               {{ $user->email}}
              </div>
            </div><br>
            <div class="row r-firstname">
              <div class="col-md-4" style="border:0px solid">
                 First Name:
              </div>
              <div class="col-md-8 profile-txt" style="border:0px solid">
                <input type="text" name="firstname" value="{{ $user->firstname}}">
              </div>
            </div><br>
            <div class="row r-lastname">
              <div class="col-md-4" style="border:0px solid">
                 Last Name:
              </div>
              <div class="col-md-8 profile-txt" style="border:0px solid">
                <input type="text" name="lastname" value="{{ $user->lastname}}">
              </div>
            </div><br>
            <div class="row r-country">
              <div class="col-md-4" style="border:0px solid">
                 Country:
              </div>
              <div class="col-md-8 profile-txt" style="border:0px solid">
                <input type="text" name="country" value="{{ $user->country}}">
              </div>
            </div><br><br>
             <button type="submit" class="btn btn-block btn-prd" id="js-save-profile">SAVE</button>
       </form>