Fixes S3 media items in bucket root folders (#3461)

FIxes #3445. Credit to @rajakhoury

modules/system/classes/MediaLibrary.php

@@ -574,7 +574,7 @@ class MediaLibrary
             ? $this->getStorageDisk()->size($path)
             : $this->getFolderItemCount($path);
 
-        $publicUrl = $this->storagePath.$relativePath;
+        $publicUrl = $this->getPathUrl($relativePath);
 
         return new MediaLibraryItem($relativePath, $size, $lastModified, $itemType, $publicUrl);
     }