IcingaObject: resolve related properties when...

...telling an object to be "unmodified"

fixes #2559

library/Director/Objects/IcingaObject.php

@@ -1536,6 +1536,8 @@ abstract class IcingaObject extends DbObject implements IcingaConfigRenderer
         foreach ($this->loadedMultiRelations as $multiRelation) {
             $multiRelation->setBeingLoadedFromDb();
         }
+        // This might trigger DB requests and 404's:
+        $this->resolveUnresolvedRelatedProperties();
 
         parent::setBeingLoadedFromDb();
     }