You can use if else:
<div class="video-embed" style="margin-top: 0px; z-index:102; margin-bottom: 0px;">
<?php
$url1 = get_post_meta( $post->ID , 'video_play' , true ) ?: get_post_meta( $post->ID , 'video_stop' , true ) ?: false;
if( $url1 ):
$search="#(.*?)(?:href="https://wordpress.stackexchange.com/questions/302040/https?://)?(?:www\.)?(?:youtu\.be/"youtube\.com(?:/embed/|/v/|/watch?.*?v=))([\w\-]{10,12}).*#x";
$replace="http://www.youtube.com/embed/$2";
$url = preg_replace($search,$replace,$url1);
?>
<iframe width="560" height="315" src="<?php echo $url; ?>" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>
<?php
else:
echo "This video is removed";
endif;
?>
</div>