Potential virus2 hotfix that raises your hopes then almost immediately dashes them

Created by: despotate

This very likely doesn't do anything to prevent the crash that happened, it just changes generate_uniqueID so that it vacates the old uniqueID when a new one is assigned so we don't get any future problems from having the proc called a lot.

Fun fact: did you know that disease2_list, the global list of diseases, doesn't actually do anything? https://github.com/d3athrow/vgstation13/search?utf8=%E2%9C%93&q=disease2_list