Set default values for site variables

good for gem-based first run

_layouts/category.html

@@ -14,11 +14,13 @@ layout: page
   </h1>
 
   <ul class="post-content pl-0">
+    {% assign post_long_df = site.data.date_format.post.long | default: '%b %e, %Y' %}
+
     {% for post in page.posts %}
     <li class="d-flex justify-content-between pl-md-3 pr-md-3">
       <a href="{{ post.url | relative_url }}">{{ post.title }}</a>
       <span class="dash flex-grow-1"></span>
-      <span class="text-muted small">{{ post.date | date: site.data.date_format.post.long }}</span>
+      <span class="text-muted small">{{ post.date | date: post_long_df }}</span>
     </li>
     {% endfor %}
   </ul>

_layouts/home.html

@@ -83,7 +83,7 @@ layout: page
       {% if post.pin %}
       <div class="pin">
         <i class="fas fa-thumbtack fa-fw"></i>
-        <span>{{ site.data.label.pin_prompt }}</span>
+        <span>{{ site.data.label.pin_prompt | default: 'Pinned' }}</span>
       </div>
       {% endif %}
 

_layouts/tag.html

@@ -7,6 +7,7 @@ layout: page
 # MIT Licensed
 ---
 
+
 <div id="page-tag">
   <h1 class="pl-lg-2">
     <i class="fa fa-tag fa-fw text-muted"></i>
@@ -14,11 +15,13 @@ layout: page
     <span class="lead text-muted pl-2">{{ page.posts | size }}</span>
   </h1>
   <ul class="post-content pl-0">
+    {% assign post_long_df = site.data.date_format.post.long | default: '%b %e, %Y' %}
+
     {% for post in page.posts %}
     <li class="d-flex justify-content-between pl-md-3 pr-md-3">
       <a href="{{ post.url | relative_url }}">{{ post.title }}</a>
       <span class="dash flex-grow-1"></span>
-      <span class="text-muted small">{{ post.date | date: site.data.date_format.post.long }}</span>
+      <span class="text-muted small">{{ post.date | date: post_long_df }}</span>
     </li>
     {% endfor %}
   </ul>