文檔上傳後不能打開網頁

文檔上傳後不能打開網頁：

Fatal error: Call to undefined function _system_theme_data() in /…/includes/theme.inc on line 439

theme.inc的437-439行為：
else {
// Scan the installation when the database should not be read.
$themes = _system_theme_data();
}