Bug Report

When I click a dropdown (type pointing without scrollbar), the scrollbar of window is not display when the content of dropdown overflow the window.
When I enable the observeChanges option of modal to true, that doesn't work the first time a click the dropdown but the second time a click, the modal is display on the top of window (strange :s) and the scrollbar appears

Expected result

Scrollbar appear properly

Actual result

Scrollbar doen't appear properly

Testcase

https://jsfiddle.net/dutrieux/sj5or8bk/27/

Screenshot (when possible)

Version

2.7.2