* log errors instead showing them to users with system directories

* now it will print a notice, and aditionally log full path into
system/logs/error.log
* also, when it fails to load config.lua it will output error also to
error.log
* fix when $_SERVER['HTTP_ACCEPT_ENCODING'] is not set.

system/libs/pot/OTS_Group.php

@@ -47,7 +47,7 @@ class OTS_Group extends OTS_Row_DAO implements IteratorAggregate, Countable
  *
  * @param DOMElement $group  Group info.
  */
-    public function __construct($data)
+    public function __construct($data = array())
     {
 		$this->data = $data;
     }