Site Icon will be shown if the article doesn't have post thumbnail. #3

css/mamahack.css

@@ -56,3 +56,6 @@
     vertical-align: middle;
     padding-right: 15px;
 }
+.p-entry__tw-follow__cont > * {
+    margin: 0;
+}

mamahack.php

@@ -51,10 +51,19 @@ public function the_content( $contents )
 		}
 		$like = '<div style="padding:10px 0px;"></div>';
 
-		if (get_option('mamahack_fb_account'))
+		if ( get_option( 'mamahack_fb_account' ) )
 		{
 			$like .= '<div class="p-entry__push">';
-			$like .= '<div class="p-entry__pushThumb" style="background-image: url(' . wp_get_attachment_url( get_post_thumbnail_id($post->ID) ). ')"></div>';
+			$like .= '<div class="p-entry__pushThumb" style="background-image: url(';
+			if ( has_post_thumbnail( $post->ID ) )
+			{
+				$like .= wp_get_attachment_image_url( get_post_thumbnail_id($post->ID), 'medium' );
+			}
+			elseif ( has_site_icon() )
+			{
+				$like .= get_site_icon_url();
+			}
+			$like .= ')"></div>';
 			$like .= '<div class="p-entry__pushLike">';
 			$like .= '<p>'._('この記事が気に入ったら<br>いいね！しよう').'</p>';
 			$like .= '<div class="p-entry__pushButton">';