« MODx Parse Error »

MODx encountered the following error while attempting to parse the requested resource:
« PHP Parse Error »
 
PHP error debug
  Error: array_key_exists() expects parameter 2 to be array, null given 
  Error type/ Nr.: Warning - 2 
  File: /usr/www/users/poweri3/poweri/manager/includes/document.parser.class.inc.php 
  Line: 1090 
  Line 1090 source: if (array_key_exists($alias, $this->documentListing)) {  
 
Parser timing
  MySQL: 0.0006 s(1 Requests)
  PHP: 0.0101 s 
  Total: 0.0107 s