add preview_image to list and post item templates

templates/pinax/blog/blog_list.html

@@ -8,9 +8,9 @@
         {% for news in object_list %}
             <div class="news__item">
                 <div class="row">
-                    {% if news.image_set.primary_image %}
+                    {% if news.post.preview_image %}
                         <div class="col-md-4 col-12">
-                            <div class="news__image"><img src="{{ news.image_set.primary_image.url }}" alt="{{ news.title }}"></div>
+                            <div class="news__image"><img src="{{ news.post.preview_image.url }}" alt="{{ news.title }}"></div>
                         </div>
                     {% endif %}
                     <div class="col-lg-6 col-md-8 col-12">

templates/pinax/blog/blog_post.html

@@ -6,9 +6,9 @@
         <div class="news">
             <div class="news__item">
                 <div class="row">
-                    {% if object.image_set.primary_image %}
+                    {% if object.post.preview_image %}
                         <div class="col-md-4 col-12">
-                            <div class="news__image"><img src="{{ object.image_set.primary_image.url }}"
+                            <div class="news__image"><img src="{{ object.post.preview_image.url }}"
                                                           alt="{{ object.title }}"></div>
                         </div>
                     {% endif %}