Add empty state for deprecations

Make it more obvious that the panel isn't broken.

Author: markstory

templates/element/deprecations_panel.php

@@ -23,6 +23,8 @@
 
 use function Cake\Core\h;
 
+$hasAny = count($app) + count($plugins) + count($cake) . count($vendor);
+
 $printer = function ($section, $data) {
 ?>
     <h3><?= h(ucfirst($section)) ?> </h3>
@@ -39,7 +41,11 @@
 }
 ?>
 <div class="c-deprecations-panel">
-    <?php
+    <?php if ($hasAny) : ?>
+        <p class="c-flash c-flash--info">No deprecations</p>
+        <?php
+    endif;
+
     if (count($app)) :
         $printer('app', $app);
     endif;