Getting error when click in my second post for the single page

When I am trying to open first post in single page, it's opening and when trying to open my second post in single page it;s showing "Trying to get property 'title' of non-object"

Here is code

FrontendController

public function singlePost($slug)
{

    $post= Post::where('slug', $slug)->first();


    return view('single')->with('post', $post)


        ->with('title', $post->title)
        ->with('settings', Setting::first())
        ->with('categories', Category::take(4)->get());

}

single.blade.php

in that I am using same frontend controller for same page @extends('layouts.frontend')

@section('content')

<div id="product-post">
    <div class="container">
        <div class="row">
            <div class="col-md-12">
                <div class="heading-section">

                    <img src="" alt="" />
                </div>
            </div>
        </div>
        <div id="single-blog" class="page-section first-section">
            <div class="container">
                <div class="row">
                    <div class="product-item col-md-12">
                        <div class="row">
                            <div class="col-md-8">

                                <div class="product-content">
                                    <div class="product-title">
                                        <h3></h3>
                                        <span class="subtitle">4 comments</span>
                                    </div>
                                    <p>
                                        {!! $post->content!!}

                                    </p>
                                </div>



                                <div class="leave-form">
                                    <form action="#" method="post" class="leave-comment">
                                        <div class="row">
                                            <div class="name col-md-4">
                                                <input type="text" name="name" id="name" placeholder="Name" />
                                            </div>
                                            <div class="email col-md-4">
                                                <input type="text" name="email" id="email" placeholder="Email" />
                                            </div>
                                            <div class="subject col-md-4">
                                                <input type="text" name="subject" id="subject" placeholder="Subject" />
                                            </div>
                                        </div>
                                        <div class="row">
                                            <div class="text col-md-12">
                                                <textarea name="text" placeholder="Comment"></textarea>
                                            </div>
                                        </div>
                                        <div class="send">
                                            <button type="submit">Send</button>
                                        </div>
                                    </form>
                                </div>
                            </div>

                        </div>
                    </div>
                </div>
            </div>
        </div>
    </div>
</div>




@endsection

via Chebli Mohamed