Call to a member function fill() on null　エラーの解消がしたい

//profileController
 public function update(Request $request)
    {
     // Validationをかける
     $this->validate($request, Profile::$rules);
     // News Modelからデータを取得する
     $profile = Profile::find($request->id);
     // 送信されてきたフォームデータを格納する
     $profile_form = $request->all();
     // 該当するデータを上書きして保存する
     $profile->fill($profile_form)->save();

        $profileHistory = new ProfileHistory;
        $profileHistory->profile_id = $profile->id;
        $profileHistory->edited_at = Carbon::now();
        $profileHistory->save();
        return redirect('admin/profile/edit');
    }

//profile/edit.blade.php
@extends('layouts.profile')

@section('title','プロフィールの編集')

@section('content')
<div class="container">
        <div class="row">
            <div class="col-md-8 mx-auto">
                <h2>プロフィールの編集</h2>
                <form action="{{ action('App\Http\Controllers\Admin\ProfileController@update') }}" method="post" enctype="multipart/form-data">

                    @if (count($errors) > 0)
                        <ul>
                            @foreach($errors->all() as $e)
                                <li>{{ $e }}</li>
                            @endforeach
                        </ul>
                    @endif
                    <div class="form-group row">
                        <label class="col-md-2">氏名</label>
                        <div class="col-md-10">
                            <input type="text" class="form-control" name="name" value="{{ $profile_form->name }}">
                        </div>
                    </div>
                    <div class="form-group row">
                        <label class="col-md-2">性別</label>
                        <div class="col-md-10">
                            <input type="text" class="form-control" name="gender" value="{{ $profile_form->gender }}">
                        </div>
                    </div>
                    <div class="form-group row">
                        <label class="col-md-2">趣味</label>
                        <div class="col-md-10">
                            <input type="text" class="form-control" name="hobby" value="{{ $profile_form->hobby }}">
                        </div>
                    </div>

                    <div class="form-group row">
                        <label class="col-md-2">自己紹介</label>
                        <div class="col-md-10">
                            <textarea class="form-control" name="introduction" rows="20">{{ $profile_form->introduction }}</textarea>
                        </div>
                    </div>

                    {{ csrf_field() }}
                    <input type="submit" class="btn btn-primary" value="更新">
                </form>
                <div class="row mt-5">
                    <div class="col-md-4 mx-auto">
                        <h2>編集履歴</h2>
                        <ul class="list-group">
                            @if ($profile_form->profileHistories != NULL)
                                @foreach ($profile_form->profileHistories as $profileHistory)
                                    <li class="list-group-item">{{ $profileHistory->edited_at }}</li>
                                @endforeach
                            @endif
                        </ul>
                    </div>
                </div>
            </div>
        </div>
    </div>
@endsection

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

class CreateProfilesTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('profiles', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->string('name');
            $table->string('gender');
            $table->string('hobby');
            $table->string('introduction');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('profiles');
    }
}

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Profile extends Model
{
    use HasFactory;
    protected $guarded = array('id');

    public static $rules = array(
        'name' => 'required',
        'gender' => 'required',
        'hobby' => 'required',
        'introduction' => 'required',
    );

    public function profileHistories()
    {
      return $this->hasMany('App\Models\ProfileHistory');

    }
}