Error with Photo Gallery Plugin

Hello,
when i try to access the plugin to change the settings i get this message:

Content - Photo Gallery Plugin

content / photogallery
Hot Photo Gallery - Commercial plugin from HotJoomlaTemplates.com


Catchable fatal error: Object of class JDocumentHTML could not be converted to string in /var/www/vhosts/velwebsolution.it/httpdocs/picone/plugins/content/photogallery/elements/loader.php on line 40

Can you help me.

Thanks
Vito Magno

Open that file, replace:

$header_media = $document->addStyleSheet(JURI::root(1) . '/plugins/content/photogallery/css/admin.css');
$header_media .= $document->addScript(JURI::root(1) . '/plugins/content/photogallery/js/jscolor.js');

with:

$document->addStyleSheet(JURI::root(1) . '/plugins/content/photogallery/css/admin.css');
$document->addScript(JURI::root(1) . '/plugins/content/photogallery/js/jscolor.js');