Navigation: Add method getActiveItem()

refs #5600

library/Icinga/Web/Navigation/Navigation.php

@@ -221,6 +221,23 @@ class Navigation implements ArrayAccess, Countable, IteratorAggregate
         return isset($this->items[$name]) ? $this->items[$name] : $default;
     }
 
+    /**
+     * Return the currently active item or the first one if none is active
+     *
+     * @return  NavigationItem
+     */
+    public function getActiveItem()
+    {
+        $firstItem = reset($this->items);
+        foreach ($this->items as $item) {
+            if ($item->getActive()) {
+                return $item;
+            }
+        }
+
+        return $firstItem->setActive();
+    }
+
     /**
      * Return this navigation's items
      *