gnome-shell crashed with SIGSEGV in _st_theme_node_ensure_background(), can't lock my screen.

[Slavo Roikhel]

Versions:
Ubuntu 20.04 LTS focal
GNOME Shell 3.36.2
gnome-screensaver 3.6.1-11ubuntu4
Using gdm3 as a display manager GDM 3.34.1

Expected:
When locking the computer it should lock it.

What happens instead:
Can't lock my screen at all with:
1) Super + L keys
2) Manually pressing 'Lock' on Menu
3)'gnome-screensaver-command -l' in the terminal

I have to Log out/ shutdown my computer at the end of the day.
In case I can't lock my screen it's a security issue.

syslog output:
Jun 1 16:47:02 slava-ubuntu gsd-media-keys[2207]: Couldn't lock screen: GDBus.Error:org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying

ProblemType: Crash
DistroRelease: Ubuntu 20.04
Package: gnome-shell 3.36.2-1ubuntu1~20.04.1
ProcVersionSignature: Ubuntu 5.4.0-33.37-generic 5.4.34
Uname: Linux 5.4.0-33-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.2
Architecture: amd64
CasperMD5CheckResult: skip
CrashCounter: 1
CurrentDesktop: ubuntu:GNOME
Date: Tue Jun 2 11:10:27 2020
DisplayManager: gdm3
ExecutablePath: /usr/bin/gnome-shell
ExecutableTimestamp: 1588817557
InstallationDate: Installed on 2019-04-14 (415 days ago)
InstallationMedia: Ubuntu 16.04.5 LTS "Xenial Xerus" - Release amd64 (20180731)
ProcCmdline: /usr/bin/gnome-shell
ProcCwd: /home/slavar
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, user)
 SHELL=/usr/bin/zsh
 XDG_RUNTIME_DIR=<set>
RelatedPackageVersions: mutter-common 3.36.2-1ubuntu1~20.04.1
SegvAnalysis:
 Segfault happened at: 0x7fde53381252 <_st_theme_node_ensure_background+226>: mov (%rax),%r12
 PC (0x7fde53381252) ok
 source "(%rax)" (0x2c005d00200020) not located in a known VMA region (needed readable region)!
 destination "%r12" ok
SegvReason: reading unknown VMA
Signal: 11
SourcePackage: gnome-shell
StacktraceTop:
 _st_theme_node_ensure_background () from /usr/lib/gnome-shell/libst-1.0.so
 st_theme_node_paint_equal () from /usr/lib/gnome-shell/libst-1.0.so
 ?? () from /usr/lib/gnome-shell/libst-1.0.so
 st_widget_style_changed () from /usr/lib/gnome-shell/libst-1.0.so
 ?? () from /usr/lib/gnome-shell/libst-1.0.so
Title: gnome-shell crashed with SIGSEGV in _st_theme_node_ensure_background()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: docker sudo wireshark
separator:

[Apport retracing service (apport)]

Thank you for taking the time to report this crash and helping to make this software better. This particular crash has already been reported and is a duplicate of bug #1877774, so is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.