laravel5.8:Creating default object from empty value

I want to show different contents depends on the category, but I got an error "Creating default object from empty value".

Now, I want to show ticket and coupon information when category_id = 1, and opening hours and regular holidays information when category_id is not 1.

How can I fix this issue? I hope someone helps me out. Thank you.

show.blade.php

@if($post->category_id= '1')
        <div class="detail-content">
            <ul class="detail-content-list">
                <li>●　Ticket</li>
                <li>Man : </li>
                <li>Woman : </li>
                <li>●　Coupon</li>
                <li>  :  <a href=""></a></li>
            </ul>
        </div>
        @else
        <div class="detail-content">
            <ul class="detail-content-list">
                <li>●　Opening Hours</li>
                <li> lorem</li>
                <li>●　Regular Hokidays</li>
                <li>lorem</li>
            </ul>
        </div>
        @endif

resultsController.php

public function show(Post $post)
{
    $slug = $post->slug;
    $recommended_posts = Post::inRandomOrder()
                        ->whereDate('date','>',date('Y-m-d'))
                        ->where('category_id','=',$post->category_id)
                        ->where('id','!=',$post->id)
                        ->limit(7)
                        ->get();


    $posts['particular_post'] = $post;
    $posts['recommended_posts'] = $recommended_posts;

    return view('posts.show',compact('posts'));
}

table

public function up()
{
    Schema::create('posts', function (Blueprint $table) {
        $table->bigIncrements('id');
        $table->string('image');
        $table->unsignedBigInteger('category_id');
        $table->string('meta');
        $table->string('alt');
        $table->string('title');
        $table->string('slug');
        $table->string('place');
        $table->string('map');
        $table->date('date');
        $table->string('organizer');
        $table->string('organizer_link');
        $table->timestamp('published_at')->nullable();
        $table->text('description');
        $table->timestamps();
    });
}

via Chebli Mohamed