Modal shifts around when scrollbar appears

[bborn]

Bug Report

A modal with a tabular menu inside (or anything else that causes the modal height to change) will shift when the height exceeds the window height, and a scrollbar appears on the browser window.

Expected result

The modal position should not change when a scrollbar is shown/hidden

Actual result

The modal position shifts slightly.

Screenshot (when possible)

[lubber-de]

Confirmed. Testcase: https://jsfiddle.net/6qpy7u83/

[lubber-de]

Fixed by #2969 See https://jsfiddle.net/lubber/yho0ecap/1/