NavigationItem: Set the parent on a child in method setChildren()

refs #5600

library/Icinga/Web/Navigation/NavigationItem.php

@@ -244,7 +244,7 @@ class NavigationItem implements Countable, IteratorAggregate
     }
 
     /**
-     * Get the item's children
+     * Return this item's children
      *
      * @return  Navigation
      */
@@ -264,7 +264,7 @@ class NavigationItem implements Countable, IteratorAggregate
     }
 
     /**
-     * Set children
+     * Set this item's children
      *
      * @param   array|Navigation  $children
      *
@@ -278,6 +278,10 @@ class NavigationItem implements Countable, IteratorAggregate
             throw new InvalidArgumentException('Argument $children must be of type array or Navigation');
         }
 
+        foreach ($children as $item) {
+            $item->setParent($this);
+        }
+
         $this->children = $children;
         return $this;
     }