init cohorts attr to NULL, and deal with empty given value.
init cohorts attr to NULL, and deal with empty given value.

dartajax/frontend,ilios/frontend,jrjohnson/frontend,dartajax/frontend,jrjohnson/frontend,djvoa12/frontend,thecoolestguy/frontend,ilios/frontend,djvoa12/frontend,thecoolestguy/frontend