Hide language switcher during batch job

Closes #3529159

project_template/web/profiles/drupal_cms_installer/theme/templates/install-page.html.twig

@@ -19,11 +19,13 @@
 
     <main class="cms-installer__main">
 
-      <select name="langcode" class="cms-installer__language-switcher">
-        {% for langcode, name in languages %}
-          <option value="{{ langcode }}">{{ name }}</option>
-        {% endfor %}
-      </select>
+      {% if languages %}
+        <select name="langcode" class="cms-installer__language-switcher">
+          {% for langcode, name in languages %}
+            <option value="{{ langcode }}">{{ name }}</option>
+          {% endfor %}
+        </select>
+      {% endif %}
 
       {% if title %}
         <h2 class="cms-installer__main-heading">{{ title }}</h2>