Conflict with Existing Project

[careerhub-source]

When Acces /blog I get Internal Server Error with the following massage Undefined variable: og (View: /resources/views/layouts/master.blade.php) In the: "/resources/views/layouts/master.blade.php" file at line: 37

Here is some code for master.blade

    `<title>{!! MetaTag::get('title') !!}</title>
{!! MetaTag::tag('description') !!}{!! MetaTag::tag('keywords') !!}

<link rel="canonical" href="{{ request()->fullUrl() }}"/>

  @if (isset($post))
	@if (isVerifiedPost($post))
		@if (config('services.facebook.client_id'))
			<meta property="fb:app_id" content="{{ config('services.facebook.client_id') }}" />
		@endif
		**{!! $og->renderTags() !!}**     ************Refer This og*************
		{!! MetaTag::twitterCard() !!}
	@endif
    @else
	@if (config('services.facebook.client_id'))
		<meta property="fb:app_id" content="{{ config('services.facebook.client_id') }}" />
	@endif
	**{!! $og->renderTags() !!}**   ************Refer This og*************
	{!! MetaTag::twitterCard() !!}
@endif
@include('feed::links')
{!! seoSiteVerification() !!}
@if (file_exists(public_path('manifest.json')))
	<link rel="manifest" href="/manifest.json">
@endif`

Why this contadict with the code of my project? How can solve this?