"Welcome Tutorial" is blank and cannot be dismissed with Esc

In GNOME Boxes 41-rc1, the "Welcome Tutorial" displayed when the app first runs is entirely blank, and cannot be closed with Esc as used to be the case. You can only close it by clicking the X. When run from a console, the following errors are shown:

(gnome-boxes:43242): Gtk-CRITICAL **: 10:25:33.839: Error building template class 'BoxesWelcomeTutorial' for an instance of type 'BoxesWelcomeTutorial': .:2:1119 Invalid object type 'BoxesWelcomeTutorialPage'

(gnome-boxes:43242): Gtk-CRITICAL **: 10:25:33.840: gtk_container_foreach: assertion 'GTK_IS_CONTAINER (container)' failed

(gnome-boxes:43242): Handy-CRITICAL **: 10:25:33.840: hdy_carousel_get_position: assertion 'HDY_IS_CAROUSEL (self)' failed

(gnome-boxes:43242): Gtk-CRITICAL **: 10:25:33.840: gtk_widget_set_opacity: assertion 'GTK_IS_WIDGET (widget)' failed

(gnome-boxes:43242): Gtk-CRITICAL **: 10:25:33.840: gtk_widget_set_opacity: assertion 'GTK_IS_WIDGET (widget)' failed

(gnome-boxes:43242): Boxes-CRITICAL **: 10:25:33.840: boxes_welcome_tutorial_page_get_color: assertion 'self != NULL' failed

(gnome-boxes:43242): Boxes-CRITICAL **: 10:25:33.840: boxes_welcome_tutorial_page_get_color: assertion 'self != NULL' failed