Merge branch 'teuto/6084-global-conf-variable' into 'develop'

fixes #6084

Closes #6084

See merge request ispconfig/ispconfig3!1425

interface/lib/app.inc.php

@@ -130,8 +130,8 @@ class app {
 
 			//* Initialize session variables
 			if(!isset($_SESSION['s']['id']) ) $_SESSION['s']['id'] = session_id();
-			if(empty($_SESSION['s']['theme'])) $_SESSION['s']['theme'] = $conf['theme'];
-			if(empty($_SESSION['s']['language'])) $_SESSION['s']['language'] = $conf['language'];
+			if(empty($_SESSION['s']['theme'])) $_SESSION['s']['theme'] = $this->_conf['theme'];
+			if(empty($_SESSION['s']['language'])) $_SESSION['s']['language'] = $this->_conf['language'];
 		}
 
 	}