更新

app/Admin/Controllers/UserController.php

@@ -123,7 +123,7 @@ class UserController extends AdminController
 
         $form->switch('status','状态')->default(1);
         $form->text('user_info.nickname','昵称');
-        $form->image('user_info.avatar','头像')->uniqueName()->saveFullUrl();
+        $form->image('user_info.avatar','头像')->uniqueName()->removable(false)->saveFullUrl();
         $form->saving(function ($res){
             dd($res->model());
         });