Default value is not showing in the "Assigned to Theme"

On admin/settings/themekey/taxonomy
The default value is not showing in the "Assigned to Theme" select box

The function taxonomy_theme_get_theme() on line 312 is not returning a value
'#default_value' => taxonomy_theme_get_theme($key, $item->$key),

Thanks for this great module.
Regards
Geoff