start survey edit iunput validation

When add multiple empty question and submit, warning is generated, but empty questions are merged.
You may want to think twice about the flatten or nested approach.
You can see many duplicated code here for items, once you change it in one place, you have to change it again in another place. The nested approach don't have to do that, and will make the template more clean and easy to understand, no more loop index.
You should use a different commit for this change.