GTK Critical Container remove assertion

[simpsus]

Gtk-CRITICAL **: gtk_container_remove: assertion `gtk_widget_get_parent (widget) == GTK_WIDGET (container) || GTK_IS_ASSISTANT (container)' failed

These pop up all over the place. Seemingly random. One pattern that seems to stick with me:

When I open and immediately close a buydialog, it dies not appear. When an asset is selected and I close the buy dialog, it appears.

There are similar issues with other applications, for example here: http://redmine.yorba.org/issues/5028
And they are alos fixed: http://redmine.yorba.org/projects/shotwell/repository/revisions/e43061340ea8f7b3ee09ef4d1c00225be53a7d7d

But the fix does not tell me anything. Given from the scenario above, maybe the "on_asset_(de)selection" methods cause the problem. But then again the only thing GUI-related happening there is the sensitivity of the button.