post categories jekyll

app/views/admin/communication/website/posts/jekyll.html.erb

@@ -3,10 +3,12 @@ title: "<%= @post.title %>"
 date: <%= @post.published_at %> UTC
 slug: "<%= @post.slug %>"
 author: "<%= @post.author_id %>"
+<% if @post.categories.any? %>
 categories:
   <% @post.categories.each do |category| %>
   - "<%= category.id %>"
   <% end %>
+<% end %>
 <% if @post.featured_image.attached? %>
 image: "<%= @post.featured_image.blob.id %>"
 <% end %>