Add missing active class for sidebars

app/Template/budget/sidebar.php

@@ -1,13 +1,13 @@
 <div class="sidebar">
     <h2><?= t('Budget') ?></h2>
     <ul>
-        <li>
+        <li <?= $this->app->getRouterAction() === 'index' ? 'class="active"' : '' ?>>
             <?= $this->url->link(t('Budget overview'), 'budget', 'index', array('project_id' => $project['id'])) ?>
         </li>
-        <li>
+        <li <?= $this->app->getRouterAction() === 'create' ? 'class="active"' : '' ?>>
             <?= $this->url->link(t('Budget lines'), 'budget', 'create', array('project_id' => $project['id'])) ?>
         </li>
-        <li>
+        <li <?= $this->app->getRouterAction() === 'breakdown' ? 'class="active"' : '' ?>>
             <?= $this->url->link(t('Cost breakdown'), 'budget', 'breakdown', array('project_id' => $project['id'])) ?>
         </li>
     </ul>