Opencart 2 extension-modification-refresh error

Hello,
i have this error in OC latest version 2x

in admin- extension-modification.. hit refresh and
Fatal error: Call to a member function getElementsByTagName() on a non-object in /home/tghn0979/public_html/oc2015/admin/controller/extension/modification.php on line 152

and at this line i have
$files = $dom->getElementsByTagName('modification')->item(0)->getElementsByTagName('file');

Could you provide more information?

For example: Did you install your extension(s) using the extension installer or did you just place the ocmod.xml file(s) in the "system" folder? How many modifications are you using?

The error you're getting could be related to a missing or incorrect tag in a modification file.