Fix notices when file not found

from beta 2 to beta 3 and I did run update.php

$feeds_importer = new stdClass;
$feeds_importer->disabled = FALSE; /* Edit this to true to make a default feeds_importer disabled initially */
$feeds_importer->api_version = 1;
$feeds_importer->id = 'node';
$feeds_importer->config = array(
'name' => 'Node import',
'description' => 'Import nodes from CSV file.',
'fetcher' => array(
'plugin_key' => 'FeedsFileFetcher',
'config' => array(
'direct' => FALSE,
),
),
'parser' => array(
'plugin_key' => 'FeedsCSVParser',
'config' => array(
'delimiter' => ',',
),
),
'processor' => array(
'plugin_key' => 'FeedsNodeProcessor',
'config' => array(
'content_type' => 'messages',
'update_existing' => '0',
'expire' => '-1',
'mappings' => array(
'0' => array(
'source' => 'title',
'target' => 'title',
'unique' => FALSE,
),
'1' => array(
'source' => 'body',
'target' => 'body',
'unique' => FALSE,
),
'2' => array(
'source' => 'published',
'target' => 'created',
'unique' => FALSE,
),
'3' => array(
'source' => 'guid',
'target' => 'guid',
'unique' => 1,
),
),
'input_format' => '0',
'author' => 0,
),
),
'content_type' => 'messages',
'update' => 0,
'import_period' => '-1',
'expire_period' => 3600,
'import_on_create' => 1,
);