« MODx Parse Error »

MODx encountered the following error while attempting to parse the requested resource:
« PHP Parse Error »
 
PHP error debug
  Error: sort() expects parameter 1 to be array, null given 
  Error type/ Nr.: Warning - 2 
  File: /web/assets/snippets/poligalerie/poligalerie.php 
  Line: 17 
  Line 17 source: sort($file_array);  
 
Parser timing
  MySQL: 0.0050 s(4 Requests)
  PHP: 0.0303 s 
  Total: 0.0354 s