gthumb locked up after clicking on video

[pleabargain]

started gthumb from CL

gthumb started
clicked on video thumbnail
gthumb locked up
video did not play

$ gthumb

(gthumb:358013): GLib-GObject-CRITICAL **: 10:32:36.334: g_object_get: assertion 'G_IS_OBJECT (object)' failed

(gthumb:358013): Gtk-CRITICAL **: 10:32:36.334: gtk_widget_get_style_context: assertion 'GTK_IS_WIDGET (widget)' failed

(gthumb:358013): Gtk-CRITICAL **: 10:32:36.334: gtk_style_context_add_class: assertion 'GTK_IS_STYLE_CONTEXT (context)' failed

(gthumb:358013): Gtk-CRITICAL **: 10:32:36.334: gtk_widget_get_events: assertion 'GTK_IS_WIDGET (widget)' failed

(gthumb:358013): Gtk-CRITICAL **: 10:32:36.334: gtk_widget_add_events: assertion 'GTK_IS_WIDGET (widget)' failed

(gthumb:358013): Gtk-CRITICAL **: 10:32:36.334: gtk_widget_set_can_focus: assertion 'GTK_IS_WIDGET (widget)' failed

(gthumb:358013): Gtk-CRITICAL **: 10:32:36.334: gtk_widget_show: assertion 'GTK_IS_WIDGET (widget)' failed

(gthumb:358013): GLib-GObject-WARNING **: 10:32:36.334: invalid (NULL) pointer instance

(gthumb:358013): GLib-GObject-CRITICAL **: 10:32:36.334: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed

(gthumb:358013): GLib-GObject-WARNING **: 10:32:36.334: invalid (NULL) pointer instance

(gthumb:358013): GLib-GObject-CRITICAL **: 10:32:36.334: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed

(gthumb:358013): GLib-GObject-WARNING **: 10:32:36.334: invalid (NULL) pointer instance

(gthumb:358013): GLib-GObject-CRITICAL **: 10:32:36.334: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed

(gthumb:358013): GLib-GObject-WARNING **: 10:32:36.334: invalid (NULL) pointer instance

(gthumb:358013): GLib-GObject-CRITICAL **: 10:32:36.334: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed

(gthumb:358013): GLib-GObject-WARNING **: 10:32:36.334: invalid (NULL) pointer instance

(gthumb:358013): GLib-GObject-CRITICAL **: 10:32:36.334: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed

(gthumb:358013): Gtk-CRITICAL **: 10:32:36.334: gtk_stack_add_named: assertion 'GTK_IS_WIDGET (child)' failed

(gthumb:358013): Gtk-CRITICAL **: 10:32:36.334: gtk_widget_show: assertion 'GTK_IS_WIDGET (widget)' failed

(gthumb:358013): Gtk-WARNING **: 10:32:36.807: Child name 'video-area' not found in GtkStack

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: gthumb 3:3.8.0-2.1build1
ProcVersionSignature: Ubuntu 5.4.0-48.52-generic 5.4.60
Uname: Linux 5.4.0-48-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.9
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Tue Oct 6 10:33:42 2020
InstallationDate: Installed on 2015-08-23 (1870 days ago)
InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
SourcePackage: gthumb
UpgradeStatus: Upgraded to focal on 2020-06-06 (121 days ago)