use of related_field with nullable fields

[Frens Jan Rumph]

Hi,

Thanks for the extension, very useful.

Ran in some issue with using related_field in combination with a nullable field though.

return escape(formatter(reduce(getattr, field_path, obj)))

The code above from adminextensions.list_display.related_field causes a 'NoneType' object has no attribute 'title' when obj is None.

This may be an issue with other methods from list_display, but I haven't tested that.

Cheers, Frens