Only clone content folder if it exists

HFP-731

h5p-default-storage.class.php

@@ -85,8 +85,10 @@ class H5PDefaultStorage implements \H5PFileStorage {
    */
   public function cloneContent($id, $newId) {
     $path = $this->path . '/content/';
+    if (file_exists($path . $id)) {
       self::copyFileTree($path . $id, $path . $newId);
     }
+  }
 
   /**
    * Get path to a new unique tmp folder.