This is the same problem that

commit 133e04fc
Author: Caolán McNamara <caolanm@redhat.com>
Date:   Wed Jun 17 09:23:32 2015 +0100

    Resolves: tdf#91880 Invalidate graphics when the gtk window is destroyed

    not just when the GtkSalFrame is dtored

tried to fix, but that just made it more unlikely to fail

Change-Id: Icba750c787adb6cd5c5ed0874ef07e6201c4cf25
(cherry picked from commit 26c32cfe)