Sortable: fix incorrect top containment for document

[maksimr]

No description provided.

[jquerybot]

Thank you for your pull request. It looks like this may be your first contribution to a jQuery Foundation project, if so we need you to sign our Contributor License Agreement (CLA).

📝 Please visit http://contribute.jquery.org/CLA/ to sign.

After you signed, the PR is checked again automatically after a minute. If there's still an issue, please reply here to let us know.

---

If you've already signed our CLA, it's possible your git author information doesn't match your CLA signature (both your name and email have to match), for more information, check the status of your CLA check.

[scottgonzalez]

Thanks for the pull request. Before we can accept this, we need a few more actions from you. Please file a bug report with an explanation of the problem along with a reduced test case that shows the problem. We also need you to sign our CLA.

Thanks.

[maksimr]

@scottgonzalez

I haven't created new issue because I have found an issue related to this problem.

Thanks