* remove assignments (issues are set to 'no category')
* reassign issues to another category (if at least an other category exists)
If no issue is assigned to the category, it's deleted silently.
git-svn-id: http://redmine.rubyforge.org/svn/trunk@733 e93f8b46-1217-0410-a6f0-8f06a7374b81
Jean-Philippe Lang