Hi, @jonpolak ... and everyone else!
This crash has been happening to me in several occasions, still on the same "Ubuntu MATE 16.04" (64-bit) installation (now on "Ubuntu 16.04.5 LTS").
Today (17 August 2018), a few minutes ago, happened the most recent crash to me. The "XsessionErrors" section of "The application Popup Notifications has closed unexpectedly." dialog box seems to have some relevant information.
Screenshot:
Textual information of "XsessionErrors" (copied from the last lines of the file "_usr_lib_mate-notification-daemon_mate-notification-daemon.1000.crash
" located in the "/var/crash" folder or directory):
XsessionErrors:
mate-session[2117]: WARNING: Unable to find provider '' of required component 'dock'
(nm-applet:2432): Gdk-CRITICAL **: gdk_window_thaw_toplevel_updates: assertion 'window->update_and_descendants_freeze_count > 0' failed
(mate-panel:2347): GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
(blueman-applet:2389): Gdk-CRITICAL **: gdk_window_thaw_toplevel_updates: assertion 'window->update_and_descendants_freeze_count > 0' failed
(mate-power-manager:2385): GLib-CRITICAL **: Source ID 51 was not found when attempting to remove it
The Mate Notification Daemon package version is still the same (1.12.1-1):
myuser@myhost:/var/crash$ grep '^Package:' _usr_lib_mate-notification-daemon_mate-notification-daemon.1000.crash
Package: mate-notification-daemon 1.12.1-1
There are the following "assertions" line in the same "_usr_lib_mate-notification-daemon_mate-notification-daemon.1000.crash
" file that may also be relevant:
myuser@myhost:/var/crash$ grep -i 'assert' _usr_lib_mate-notification-daemon_mate-notification-daemon.1000.crash
Ago 17 08:20:13 myhost NetworkManager[1212]: nm_device_get_device_type: assertion 'NM_IS_DEVICE (self)' failed
Ago 17 08:21:18 myhost org.blueman.Mechanism[1162]: (blueman-mechanism:3021): Gtk-CRITICAL **: gtk_icon_theme_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed
Ago 17 08:21:55 myhost org.freedesktop.Notifications[2440]: (mate-notification-daemon:3075): GLib-GObject-CRITICAL **: g_value_get_int: assertion 'G_VALUE_HOLDS_INT (value)' failed
Ago 17 08:21:58 myhost org.freedesktop.Notifications[2440]: (mate-notification-daemon:3163): GLib-GObject-CRITICAL **: g_value_get_int: assertion 'G_VALUE_HOLDS_INT (value)' failed
(nm-applet:2618): Gdk-CRITICAL **: gdk_window_thaw_toplevel_updates: assertion 'window->update_and_descendants_freeze_count > 0' failed
(blueman-applet:2588): Gdk-CRITICAL **: gdk_window_thaw_toplevel_updates: assertion 'window->update_and_descendants_freeze_count > 0' failed
I searched for related bugs in Launchpad and I found the following bug, BUT it's for Ubuntu 18.10 (and not for 16.04) and it's for "mate-notification-daemon" version 1.20.1-1 (instead of 1.12.1-1):
This issue seems to be quite "challenging" to troubleshoot.