Error message

• Warning: class_implements(): object or string expected in file_get_stream_wrappers() (line 136 of /production/drupal/dim_prod/drupal/d7cl4/prod/uninsubria/releases/5/web/includes/file.inc).
• Warning: in_array() expects parameter 2 to be array, boolean given in file_get_stream_wrappers() (line 136 of /production/drupal/dim_prod/drupal/d7cl4/prod/uninsubria/releases/5/web/includes/file.inc).