fixed credit

app/assets/stylesheets/extranet/pages/_posts.sass

 .posts-show header figure
     display: inline-block
     position: relative
-    &::after
+    &.with-credit::after
         bottom: 0
         content: '©'
         padding: 0.5rem

app/views/extranet/posts/posts/show.html.erb

@@ -2,7 +2,7 @@
 
 <% content_for :header_right do %>
   <% if @post.featured_image.attached? %>
-    <figure>
+    <figure <% if !@post.featured_image_credit.blank? %>class="with-credit"<% end %>>
       <%= kamifusen_tag @post.featured_image, class: 'img-fluid', width: 300 %>
       <% if !@post.featured_image_credit.blank? %>
         <figcaption tabindex="0">