/usr/bin/gnome-shell:11:st_focus_manager_remove_group:g_closure_invoke:signal_emit_unlocked_R:g_signal_emit_valist:g_signal_emit

[errors.ubuntu.com bug bridge]

The Ubuntu Error Tracker has been receiving reports about a problem regarding gnome-shell. This problem was most recently seen with package version 40.2-1ubuntu1, the problem page at https://errors.ubuntu.com/problem/a7fed12980ff951be9a10c4f2e04d99a23b010ae contains more details, including versions of packages affected, stacktrace or traceback, and individual crash reports.
If you do not have access to the Ubuntu Error Tracker and are a software developer, you can request it at http://forms.canonical.com/reports/.