[#220] Make Deployments section conditional on having content in lang

This will hide the section for Japanese documentation until there is
a translation available.

- See #651 (comment)

docs/_includes/sidebar.html

@@ -60,17 +60,19 @@
   </ul>
   <!--End (temporary) beta sections-->
 
-  <ul class="sidebar-section">
-    <a href="{{ site.url | append: site.baseurl | append: localized_base_url }}/deployments">
-      <li class="title">{{ site.t[page.lang].deployments }}</li>
-    </a>
-    {% assign deployments_sections = site.deployments | sort: "order" | where: "lang", page.lang %}
-    {% for section in deployments_sections %}
-      <a href="{{ site.url | append: site.baseurl | append: localized_base_url }}/deployments/{{ section.slug }}">
-        <li>{{section.title}}</li>
+  {% assign deployments_sections = site.deployments | sort: "order" | where: "lang", page.lang %}
+  {% if deployments_sections.size > 0 %}
+    <ul class="sidebar-section">
+      <a href="{{ site.url | append: site.baseurl | append: localized_base_url }}/deployments">
+        <li class="title">{{ site.t[page.lang].deployments }}</li>
       </a>
-    {% endfor %}
-  </ul>
+      {% for section in deployments_sections %}
+        <a href="{{ site.url | append: site.baseurl | append: localized_base_url }}/deployments/{{ section.slug }}">
+          <li>{{section.title}}</li>
+        </a>
+      {% endfor %}
+    </ul>
+  {% endif %}
 
   <ul class="sidebar-section">
     {% assign tutorials = site.tutorials | where: "lang", page.lang | where_exp: "tutorial", "tutorial.order > 0" %}