修复更新插件没有权限addons文件夹

@@ -268,12 +268,16 @@ class Addon extends Backend
     public function upgrade()
     {
         $name = $this->request->post("name");
+        $addonTmpDir = RUNTIME_PATH . 'addons' . DS;
         if (!$name) {
             $this->error(__('Parameter %s can not be empty', 'name'));
         }
         if (!preg_match("/^[a-zA-Z0-9]+$/", $name)) {
             $this->error(__('Addon name incorrect'));
         }
+        if (!is_dir($addonTmpDir)) {
+            @mkdir($addonTmpDir, 0755, true);
+        }
         try {
             $uid = $this->request->post("uid");
             $token = $this->request->post("token");