Gtk-CRITICAL **: gtk_widget_event: assertion 'WIDGET_REALIZED_FOR_EVENT (widget, event)' failed

xfce4-taskmanager 1.5.1

Steps to reproduce:

1. Start xfce4-taskmanager in a terminal

Output:

Gtk-CRITICAL **: gtk_widget_event: assertion 'WIDGET_REALIZED_FOR_EVENT (widget, event)' failed