Fix topics in the events mixin
Fix topics in the events mixin

There was a variable name collision after the change from disciplines
to topics.

stopfstedt/frontend,jrjohnson/frontend,thecoolestguy/frontend,ilios/frontend,stopfstedt/frontend,gabycampagna/frontend,thecoolestguy/frontend,gboushey/frontend,ilios/frontend,gabycampagna/frontend,dartajax/frontend,jrjohnson/frontend,gboushey/frontend,dartajax/frontend,djvoa12/frontend,djvoa12/frontend