Following the bug Bug #2163496 “gnome-shell 51.alpha crashed with SIGSEGV in g_lis...” : Bugs : mutter package : Ubuntu I installed the updated packages from proposed using apt:
Commandline: apt install -t stonking-proposed mutter-common-bin --install-recommends Requested-By: corrado (1000) Upgrade: mutter-common-bin:amd64 (51~alpha-0ubuntu2, 51~beta-1ubuntu1), mutter-common:amd64 (51~alpha-0ubuntu2, 51~beta-1ubuntu1)
so i lost my desktop. I was unable to recover so i reinstalled the system and installed the updated packages from proposed via synaptic:
Commandline: /usr/sbin/synaptic
Requested-By: corrado (1000)
Upgrade: mutter-common-bin:amd64 (51~alpha-0ubuntu2, 51~beta-1ubuntu1), mutter-common:amd64 (51~alpha-0ubuntu2, 51~beta-1ubuntu1), gnome-shell:amd64 (51~alpha-0ubuntu4, 51~beta-0ubuntu1), gir1.2-mutter-51:amd64 (51~alpha-0ubuntu2, 51~beta-1ubuntu1), gnome-shell-common:amd64 (51~alpha-0ubuntu4, 51~beta-0ubuntu1), libmutter-51-0:amd64 (51~alpha-0ubuntu2, 51~beta-1ubuntu1)
This time the upgrade was ok and my system works fine.
I think the problem was due to apt not finding all the related packages but added only mutter-common.