--- page.tpl.php
+++ (clipboard)
@@ -72,9 +72,11 @@
         </a>
       <?php endif; ?>
       
-      <nav id="navbar" role="navigation">
-        <?php print drupal_render(menu_tree_output(menu_tree_page_data('main-menu'))); ?>
-      </nav>
+      <?php if ($main_menu): ?>
+        <nav id="navbar" role="navigation">
+          <?php print drupal_render(menu_tree_output(menu_tree_page_data('main-menu'))); ?>
+        </nav>
+      <?php endif; ?>
 
     </div>
   </header>