!28 将文件检查函数改为 is_file

Merge pull request !28 from F4NNIU/chk_install_lock

@@ -16,7 +16,7 @@
 define('APP_PATH', __DIR__ . '/../application/');
 
 // 判断是否安装FastAdmin
-if (!file_exists(APP_PATH . 'admin/command/Install/install.lock'))
+if (!is_file(APP_PATH . 'admin/command/Install/install.lock'))
 {
     header("location:./install.php");
     exit;

@@ -14,7 +14,7 @@
 define('APP_PATH', __DIR__ . '/../application/');
 
 // 判断是否安装FastAdmin
-if (!file_exists(APP_PATH . 'admin/command/Install/install.lock'))
+if (!is_file(APP_PATH . 'admin/command/Install/install.lock'))
 {
     header("location:./install.php");
     exit;