Group permissions dropdown hangs the app

Keybase GUI Version: 2.1.2-20180625190314+836e4aeaca

I just created a group and am adding users. When I get to the `Add` modal, there is a dropdown with the text, "[username] will be added as a ( Writer )". If I click on the `Writer` dropdown, I can no longer do anything in the app. It freezes/hangs/is just generally unresponsive. It looks like another modal has opened underneath which has taken the focus but without being visible. So it is probably an issue of an invisible layer that is not accessible but has focus. Quitting from the Keybase menu does not actually quit, instead I have to quit from the menu bar helper.

Reproduce the problem in the Add modal by opening the Writer dropdown in Keybase GUI 2.1.2, then verify whether the app becomes unresponsive and whether quitting from the Keybase menu fails. Trace the Add modal, Writer dropdown, and menu bar helper entry points; done means the dropdown remains usable and the application can quit normally.

Written by the indexing model from the issue text.