though not able to reproduce, I have an in-house complaint similar to

commit f120abb4
Author: Caolán McNamara <caolanm@redhat.com>
Date:   Wed Jun 8 11:35:15 2016 +0100

    Resolves: rhbz#1343766 a11y queries during dispose trigger combobox crashes

except with a listbox in the bt

Change-Id: Id31561e009a1f0ec9272a0e7216296e4017e5688