wnck-applet (window list, workspace switcher) crashes on moving/removing applet

[Dave H]

Metal install of Mate Beta 1.
Hardware: HP ENVY Sleekbook 6-1006sa ( https://gist.github.com/anonymous/b02b59d6832ef64c4fa7 )
Booted. did updates 9am 11/03/16, rebooted.
Deleted components of bottom panel. Did get a strange pop up saying workspace switcher had stopped unexpectedly, selected leave closed.
Removed bottom panel.
Selected top panel and changed properties to vertical, right orientation.
Top panel already had system monitor added with all items except swap displayed.
Was just right mouse button checking all items to see if locked in position when panel crash occurred.
(This is my second panel crash, 1st bug log failed due to lack of stack trace.)

ProblemType: Crash
DistroRelease: Ubuntu 16.04
Package: mate-panel 1.12.2-1
ProcVersionSignature: Ubuntu 4.4.0-11.26-generic 4.4.4
Uname: Linux 4.4.0-11-generic x86_64
ApportVersion: 2.20-0ubuntu3
Architecture: amd64
CurrentDesktop: MATE
Date: Fri Mar 11 08:43:49 2016
ExecutablePath: /usr/lib/mate-panel/wnck-applet
InstallationDate: Installed on 2016-03-07 (3 days ago)
InstallationMedia: Ubuntu-MATE 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160224)
ProcCmdline: /usr/lib/mate-panel/wnck-applet
ProcEnviron:
 SHELL=/bin/bash
 XDG_RUNTIME_DIR=<set>
 PATH=(custom, no user)
 LANGUAGE=en_GB:en
 LANG=en_GB.UTF-8
SegvAnalysis:
 Segfault happened at: 0x7fedfb47591b <g_type_check_instance_cast+75>: movzbl 0x16(%rdx),%eax
 PC (0x7fedfb47591b) ok
 source "0x16(%rdx)" (0x41d7894956415756) not located in a known VMA region (needed readable region)!
 destination "%eax" ok
SegvReason: reading unknown VMA
Signal: 11
SourcePackage: mate-panel
StacktraceTop:
 g_type_check_instance_cast () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
 ?? ()
 ?? ()
 g_cclosure_marshal_VOID__STRINGv () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
 ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
Title: wnck-applet crashed with SIGSEGV in g_type_check_instance_cast()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
XsessionErrors:
 mate-session[1545]: WARNING: Unable to find provider '' of required component 'dock'
 (nm-applet:1871): Gdk-CRITICAL **: gdk_window_thaw_toplevel_updates: assertion 'window->update_and_descendants_freeze_count > 0' failed

[Apport retracing service (apport)]

StacktraceTop:
 g_type_check_instance_cast () from /tmp/apport_sandbox_OBehfA/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
 pager_update ()
 display_workspace_names_changed ()
 g_cclosure_marshal_VOID__STRINGv () from /tmp/apport_sandbox_OBehfA/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
 _g_closure_invoke_va () from /tmp/apport_sandbox_OBehfA/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0

[Launchpad Janitor (janitor)]

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

[Vlad Orlov (monsta)]

Random crashes of wnck-applet in various functions on moving/removing the applet are now fixed upstream in 1.18.6.

https://github.com/mate-desktop/mate-panel/commit/86c64efc423448dfb3d069ba3b701bdae6c7db10

[Martin Wimpress  (flexiondotorg)]

Fixed in mate-panel 1.18.6-1