gnome-screensaver crashed with SIGSEGV in XGetScreenSaver → disable_builtin_screensaver → watchdog_timer → g_timeout_dispatch → g_main_dispatch

[Nicolas_Raoul]

Today I upgraded from Ubuntu 2016.04.1 LTS with "sudo do-release-upgrade -d"
I also switch back from Gnome to Ubuntu's default desktop environment, which I had left about a year ago because of bugs.
Now Ubuntu seems to be working fine, but I received this error report out of nowhere.

Instance on errors.u.c
https://errors.ubuntu.com/problem/db9f31c05086077179fffc889aa4fa02c8e57f46

ProblemType: Crash
DistroRelease: Ubuntu 18.04
Package: gnome-screensaver 3.6.1-8ubuntu1
ProcVersionSignature: Ubuntu 4.13.0-25.29-generic 4.13.13
Uname: Linux 4.13.0-25-generic x86_64
ApportVersion: 2.20.8-0ubuntu6
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Mon Jan 22 16:18:38 2018
EcryptfsInUse: Yes
ExecutablePath: /usr/bin/gnome-screensaver
InstallationDate: Installed on 2016-03-21 (672 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
ProcCmdline: /usr/bin/gnome-screensaver --no-daemon
Signal: 11
SourcePackage: gnome-screensaver
StacktraceTop:
 XGetScreenSaver () at /usr/lib/x86_64-linux-gnu/libX11.so.6
 ()
 () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
 g_main_context_dispatch () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
 () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
Title: gnome-screensaver crashed with SIGSEGV in XGetScreenSaver()
UpgradeStatus: Upgraded to bionic on 2018-01-22 (0 days ago)
UserGroups: adm cdrom dialout dip lpadmin plugdev sambashare sudo wireshark

[Apport retracing service (apport)]

StacktraceTop:
 XGetScreenSaver (dpy=0x55c1a201a900, timeout=timeout@entry=0x7ffe362832d8, interval=interval@entry=0x7ffe362832dc, prefer_blanking=prefer_blanking@entry=0x7ffe362832e0, allow_exp=allow_exp@entry=0x7ffe362832e4) at ../../src/GetSSaver.c:44
 disable_builtin_screensaver (unblank_screen=0, watcher=<error reading variable: value has been optimized out>) at gs-watcher-x11.c:539
 watchdog_timer (watcher=<error reading variable: value has been optimized out>) at gs-watcher-x11.c:609
 g_timeout_dispatch (source=source@entry=0x55c1a21638d0, callback=<optimized out>, user_data=<optimized out>) at ../../../../glib/gmain.c:4633
 g_main_dispatch (context=0x55c1a2024fd0) at ../../../../glib/gmain.c:3148

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Nicolas_Raoul (nicolas-raoul)]

Just got the same error again.