Dot dialog dropdown is missing scrollbars

1) Go to any JIRA view issue page.
2) Scroll down the page.
3) Press "." then down-arrow to trigger the dot dialog menu.
The menu does not have scrollbars and you can't access the items that have fallen off the bottom of the screen.

This reproduces in all browsers.
It is specific to the current location of the viewport, in particular, whether the stalker bar is fixed or stalking.

Please speak to Sean when working on this as he understands the layout maths.