file engine bug when fileCache::delete

LINE: 111
foreach ($files as $file) {
if ($fp = fopen($file, 'w')) {
// only delete the cache file once we obtain an exclusive lock to prevent
// deleting a cache file that is currently being read.
if (flock($fp, LOCK_EX)) {
unlink($file);
}
}

we should replace $file with $file->filename, because file_scan_directory() returns object