I have the same error,

Undefined subroutine &main::do_nothing called at /home/......./public_html/sql/php/admin/GT/Plugins.pm line 102

I installed 2.1 and imported a 2.03 db

I added contact_email and contact_name fields to links tables

The field category_template was present, I did not need to add.

I have 3 categories, only 2 categories contains records before importing.
After import all links was copied in 1 category.

Michael

--
Michael Skaide

http://www.cycle24.de